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Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/animallocomotion00univ_0 


Animal  Locomotion. 


THE 

MUYBRIDGE  WORK 

AT  THE 

UNIVERSITY  OF  PENNSYLVANIA. 


THE  METHOD  AND  THE  RESULT. 


PRINTED  FOR  THE  UNIVERSITY". 


J.  B.  LIPPINCOTT  COMPANY, 

PUILADEL  P II I A. 


188  8. 


Copyright,  1888,  by  The  University  of  Pennsylvania. 


CONTENTS. 

PAGE 

Note 5 

The  Mechanism  of  Instantaneous  Photography.  By  William 

Dennis  Marks , Ph.B.C.E 9 

Materials  for  a Memoir  on  Animal  Locomotion.  By  Harrison 

Allen , M.D 35 

A Study  of  some  Normal  and  Abnormal  Movements  Photo- 
graphed by  Muybridge.  By  Francis  X.  Dercum,  M.D. , Ph.D.  103 


3 


NOTE. 


It  is  fitting  that  a few  words  should  be  said  here  in  regard  to 
the  connection  of  the  University  with  this  work,  and  the  motives 
which  led  its  authorities  to  assume  the  supervision  of  it. 

The  function  of  a university  is  not  limited  to  the  mere  instruc- 
tion of  students.  Researches  and  original  investigations  con- 
ducted by  the  mature  scholars  composing  its  faculties  are  an 
important  part  of  its  work,  and  in  a larger  conception  of  its  duty 
should  be  included  the  aid  which  it  can  extend  to  investigators 
engaged  in  researches  too  costly  or  elaborate  to  be  accomplished 
by  private  means. 

When  ample  provision  is  made  in  these  several  directions  we 
shall  have  the  university  adequately  equipped  and  prepared  to 
exert  fully  her  great  function  as  a discoverer  and  teacher  of  truth. 

This  book  is  the  result  of  an  unusually  elaborate  investigation 
thus  conducted  during  the  past  four  years  under  the  auspices  of 
the  University  of  Pennsylvania.  In  1883  it  was  found  that  Mr. 
E.  Muybridge,  who  was  the  first  successfully  to  apply  instantane- 
ous photography  to  the  study  of  Animal  Motion,  had  long  cher- 
ished the  desire  of  making  a new  and  greatly  extended  study  of 
the  subject,  but  had  been  deterred  by  the  want  of  means.  An 
extensive  photographic  plant,  elaborate  electrical  and  mechanical 
apparatus,  access  to  typical  animals  of  many  kinds,  much  space  for 
the  erection  of  laboratories,  and  a large  fund  for  current  expenses 
were  needed. 

It  was  represented  to  the  Trustees  of  the  University  that  sev- 
eral individuals,  appreciating  the  importance  of  the  proposed 
work  to  art  and  science,  would  unite  in  guaranteeing  all  expenses 
connected  with  the  investigation  if  a University  Commission  should 


6 


NOTE. 


be  appointed  to  supervise  the  entire  affair,  and  thus  insure  its 
thoroughly  scientific  character. 

In  March,  1884,  the  following  Commission  was  appointed  for 
the  above  purpose : 

William  Pepper,  M.D.,  LL.D. 

Joseph  Leidy,  M.D.,  LL.D.,  Professor  of  Anatomy. 

George  F.  Barker,  M.D.,  Professor  of  Physics. 

Rush  Shippen  Huidekoper,  M.D.,  Professor  of  Veterinary 
Anatomy  and  Pathology. 

William  D.  Marks,  Whitney  Professor  of  Dynamical  Engi- 
neering. 

Lewis  M.  Haupt,  Professor  of  Civil  Engineering. 

Thomas  C.  Eakins,  of  the  Academy  of  Fine  Arts. 

Edward  H.  Coates,  Chairman  of  the  Instruction  Committee  at 
Academy  of  Fine  Arts,  Chairman. 

Harrison  Allen,  M.D.,  Emeritus  Professor  of  Physiology, 
Secretary. 

The  investigation  proved  even  more  prolonged  and  costly  than 
had  been  anticipated,  and  more  than  three  years  elapsed  and  nearly 
thirty  thousand  dollars  were  expended  before  its  completion. 

The  result  has,  however,  fully  justified  the  action  of  the  Uni- 
versity, as  well  as  the  expenditure  of  time  and  money;  the  work 
will  undoubtedly  be  of  lasting  service  to  art  and  science. 

Special  mention  should  be  made  of  the  valuable  assistance  ren- 
dered by  the  authorities  of  the  Zoological  Gardens,  and  particularly 
by  Mr.  Arthur  E.  Brown,  the  superintendent,  who  extended  every 
facility  to  Mr.  Muybridge  in  photographing  many  typical  animals 
in  their  splendid  collection.  It  is  due  to  Dr.  F.  X.  Dercum  that 
acknowledgment  should  be  made  here  of  the  great  amount  of  time 
and  labor  devoted  by  him  to  furthering  the  success  of  this  inves- 
tigation. 

The  mass  of  novel  material  presented  in  this  work  is  so  great 
that  it  has  not  as  yet  been  possible  to  subject  any  considerable 


NOTE. 


7 


portion  of  it  to  critical  examination.  As,  however,  the  sole  ob- 
ject which  induced  the  University  to  assume  supervision  of  this 
work  was  to  contribute  to  the  scientific  study  of  animal  motions, 
it  has  been  decided  to  publish  in  the  present  form  a brief  descrip- 
tion by  Professor  W.  D.  Marks,  Whitney  Professor  of  Dynam- 
ical Engineering  in  the  University  of  Pennsylvania,  of  the  appa- 
ratus and  methods  employed ; a memoir  by  Dr.  Harrison  Allen, 
Emeritus  Professor  of  Physiology  in  the  University  of  Pennsyl- 
vania, on  some  of  the  laws  or  principles  elucidated  by  Mr.  Muy- 
bridge’s photographs;  and  an  article  on  the  clinical  aspects  of 
certain  nervous  affections  as  illustrated  by  instantaneous  photog- 
raphy, by  Dr.  F.  X.  Dercum,  Instructor  in  Nervous  Diseases  in 
the  University  of  Pennsylvania. 


William  Pepper,  Provost. 


THE  MECHANISM 


OF 

INSTANTANEOUS  PHOTOGRAPHY. 

BY 

WILLIAM  DENNIS  MARKS,  Ph.B.C.E., 

WHITNEY  PROFESSOR  OF  DYNAMICAL  ENGINEERING  UNIVERSITY  OF  PENNSYLVANIA. 


A careful  search  through  the  files  of  the  British  Journal  of 
Photography , The  Photographic  News,  and  other  analogous  papers, 
reveals  such  an  endless  variety  of  ingenious  devices  for  instanta- 
neous shutters  and  their  appurtenances  as  will  at  once  prevent 
even  an  attempt  at  a chronological  reference  to  them. 

We  are  forced,  by  lack  of  space,  to  content  ourselves  by  refer- 
ring those  interested  to  these  papers,  and  to  the  published  writings 
of  Marey,  Pickering,  and  Bowditch. 

In  the  brief  description  of  Professor  Eakins’s  apparatus,  here- 
after given,  we  have  all  that  Marey  has  used,  with  additions 
perfecting  it  greatly. 

Professor  Pickering  has  published  two  interesting  papers  on 
instantaneous  photography.  One  is  published  in  the  Proceedings 
of  the  American  Academy  of  Science,  January  14, 1885;  the  other, 
describing  a tuning-fork  method  of  measuring  exposures,  was  pub- 
lished in  Science,  November  14,  1884.  It  is,  however,  with  the 
work  of  Mr.  Eadweard  Muy bridge  we  shall  principally  concern 
ourselves.  His  work,  covering  a period  of  years  and  involving 
an  almost  incredible  amount  of  pertinacious  labor,  required  on 
his  part,  and  the  part  of  the  committee  and  his  assistants,  the  cre- 
ation of  an  elaborate  and  complicated  series  of  machines,  hitherto 
untried  or  tried  unsuccessfully,  and  which,  furthermore,  demanded 
that  skill  on  their  part  that  can  only  come  from  long  practice  in 
their  use. 

No  small  part  of  the  success  of  this  work  is  due  to  the  patience 

9 


10 


THE  MECHANISM  OF 


and  skill  of  one  of  his  principal  assistants,  Mr.  Lino  F.  Rondi- 
nella,  and  it  is  to  him  that  the  writer  is  indebted  for  the  descrip- 
tions, drawings,  and  diagrams  of  the  apparatus  used.  Most  of 
the  work  done  in  instantaneous  photography  has  been  of  an  un- 
systematic and  desultory  nature  and  limited  scope.  In  this  work, 
which  still  leaves  much  to  be  done,  we  have  the  first  systematic 
attempt  to  record  the  motions  of  a variety  of  animals. 

Professor  Thomas  Eakins,  director  of  the  Pennsylvania  Academy 
of  the  Fine  Arts,  undertook,  under  the  auspices  of  the  University 
of  Pennsylvania,  an  investigation  of  some  mechanisms  of  animal 
movement,  in  which  he  is  much  interested.  His  apparatus  will 
be  of  great  interest.  He  chose  as  his  principal  means  the  photo- 
graphic method  of  Professor  Marey,  of  France.  The  object  to 
be  studied  is  moved  in  sunlight  before  a dark  background,  pre- 
ferably a deep  recess  painted  black.  A photographic  camera 
is  set  up.  A disk  with  one  or  more  openings  in  it  is  rapidly 
revolved  in  front  of  the  lens.  While  the  opening  is  passing 
the  lens  the  moving  object  is  photographed ; then  darkness  in 
the  camera  until  an  opening  again  arrives.  The  moving  object 
has  now  a new  position,  and  is  photographed  anew  on  the  same 
plate,  and  so  on  again  and  again  as  often  as  required,  or  until 
the  object  has  moved  beyond  the  range  of  the  lens  or  plate.  On 
the  same  plate  is  then  developed  a series  of  images  easily  com- 
pared. With  the  present  sensitiveness  of  the  gelatin  dry  plate 
a tolerably  good  image  may  be  had  of  any  light  object  moving  in 
the  sunlight  not  too  fast.  If  the  object  moves  too  fast,  the  speed 
at  which  the  opening  passes  the  lens  must  be  increased,  or  the 
opening  itself  narrowed,  either  of  which  diminishes  the  amount 
of  available  light,  and  the  image  becomes  weak. 

So  in  adjusting  the  instrument  for  a contemplated  fast  move- 
ment one  must  choose  somewhere  between  an  image  weak  but 
sharp  and  an  image  strong,  but  blurred  from  the  movement. 

A brief  description  of  the  whole  apparatus  as  used  by  Mr. 
Eakins  may  be  interesting  to  the  physiologists  who  may  wish  to 
avail  themselves  of  this  modern  instrument  of  research. 

Instead  of  one  large  disk,  as  in  Professor  Marey’s  apparatus,  he 
used  two  small  ones  on  the  same  arbor,  but  geared  at  different  rates 
of  speed, — namely,  one  to  eight. 

If  a clock-face  should  have  disks  instead  of  hands,  and  the 


INSTANTANEOUS  PHOTOGRAPHY. 


11 


openings  were  made  in  the  disks  where  the  hands  should  be,  and 
a camera  lens  placed  behind  the  noon-mark  of  the  clock,  an  image 
would  be  got  at  twelve  o’clock.  The  fast  disk  would  return  its 
opening  in  an  hour,  but  the  two  openings  would  not  coincide  till 
5t5t  minutes  past  one,  which  would  be  past  the  lens. 

The  two  disk  openings  would  again  come  together  at  10^-  min- 
utes past  two,  but  the  three  openings  and  those  in  the  disks  and  of 
the  lens  would  not  coincide  till  twelve  o’clock,  when  another  image 
could  be  impressed. 

The  disks  were  circular  saw-blades  with  four  balanced  openings, 
over  which  openings  gossamer  waterproof  was  stuck  by  Venice 
turpentine,  thickened  by  heat  and  spread  on  the  edges.  In  this 
waterproof  openings  were  cut  radially  as  wanted. 

A crank  turned  by  hand  communicated  to  the  disks  through  a 
belt  going  from  a large  to  a small  pulley  the  requisite  speed. 

Between  the  disks  and  the  lens  was  fitted  an  electric  shutter. 
The  disks  revolving,  and  the  object  set  in  motion,  the  observer, 
with  his  fingers  on  the  key-board,  presses  the  first  button  when 
he  wishes  the  impressions  to  begin,  and  the  second  button  when 
he  wishes  them  to  end. 

Pressing  the  first  button  breaks  contact  in  an  electric  circuit 
that  holds  against  the  force  of  a rubber  spring,  the  armature  of  an 
electro-magnet  controlling  the  trigger,  which  releases  in  the  shutter 
an  opaque  slide  covering  the  lens  opening.  The  second  button  of 
the  key-board  releases  in  the  same  way  a similar  opaque  slide, 
which,  having  been  held  in  place  above  the  lens,  now  comes  down 
in  front  of  it. 

The  shutter  was  constructed  to  move  very  rapidly.  The  slides 
are  little  squares  of  silk  waterproof,  kept  stretched  by  pieces  of 
quill,  silk  wrapped,  attached  to  the  corners.  These  quills  slide 
vertically,  on  brass  rods,  and  the  slides  are  pulled  down  by  india- 
rubber  bands,  which  reach  down  all  the  way  to  the  floor.  The 
bands  used  are  the  little  parcels  bands,  looped  end  to  end  until 
sufficient  length  is  got. 

The  reason  for  using  long  bands  is  this : friction  overcome, 
rapidity  is  got  from  length,  not  thickness  of  spring.  For  in- 
stance, two  gum  bands,  side  by  side,  stretched  and  released, 
would  not  travel  faster  than  one  of  them ; but  if  looped  end 
to  end  the  speed  of  the  one  adds  itself  to  the  speed  of  the  other. 


12 


THE  MECHANISM  OF 


A piece  of  catgut  arrests  the  action  of  the  spring  without 
drawing  taut  the  adjusted  strings  which  pull  down  the  slides. 

The  closed  circuit  was  used  for  the  shutter,  that  no  time  should 
be  lost  by  the  magnet  reaching  for  the  armature  and  because  less 
battery  power  would  be  required. 

In  the  camera  a new  precaution  was  taken  against  extraneous 
light, — a moving  diaphragm  immediately  in  front  of  the  plate, 
and  connected  with  a peep-sight  above  the  camera.  An  assistant 
having  adjusted  the  diaphragm  somewhat  larger  than  the  image 
to  be  photographed,  and  having  placed  his  eye  to  the  hind  sight, 
follows  the  moving  object  by  keeping  it  between  the  two  front 
sights,  the  front  sights  being  at  a distance  from  the  hind  sight 
equal  to  the  conjugate  focus  of  the  lens. 

The  plate  itself  can  also  be  slid  right  and  left  by  the  frame 
which  carries  it,  in  case  successive  poses  may  be  executed  in  one 
place  and  their  images  are  desired  on  one  plate. 

To  increase  the  range  of  the  instrument,  a second  camera  was 
devised  for  investigating  the  class  of  movement  in  one  place,  as 
that  of  a man  throwing  a stone,  where,  in  the  Marey  camera,  the 
images  would  superimpose. 

In  this  camera  the  plate  is  revolved  on  a frame  at  the  end  of 
an  axle,  which  pierces  the  back  of  the  camera. 

Belting  and  pulleys  connect  the  movement  of  the  disks  and 
of  the  plate,  and  a pair  of  friction-wheels  allows  such  an  ad- 
justment of  speed  from  the  disks  to  the  sensitive  plate  that  the 
images  may  be  made  just  to  clear  one  another. 

To  use  this  camera  the  ground  glass  is  set  true  by  adjusting 
screws  and  the  lens  focused.  A ten  by  twelve  inch  plate  or 
smaller  is  cut  to  an  octagon  and  replaces  the  ground  glass,  being 
sprung  up  against  the  adjusting  screws.  The  distance  of  the 
images  apart  having  been  determined  upon  in  degrees  when  the 
ground  glass  was  in,  the  speed  of  the  plate  is  now  adjusted.  A 
style  on  the  armature  of  an  electro-magnet  in  the  exposure- 
counting circuit  dots  on  a smoked  disk,  whose  rim  is  graduated, 
the  different  exposures  as  the  machine  is  turned.  The  sliding- 
bar  carrying  one  of  the  friction-wheels  is  pushed  in  or  out  until 
the  dots  become  the  requisite  number  of  degrees  apart. 

A moving  diaphragm  is  also  attached  to  this  camera,  having  a 
slight  horizontal  movement  and  governed  by  a peep-sight. 


INSTANTANEOUS  PHOTOGRAPHY. 


13 


For  recording  the  times  and  durations  of  exposure  a chrono- 
graph was  used,  which  had  been  designed  by  the  writer  for 
the  University  of  Pennsylvania.  An  electric  current  vibrating  a 
tuning-fork  in  the  usual  manner,  an  electro-magnet  with  a style 
to  its  armature  in  the  same  current,  on  the  smoked  paper  on  the 
turning  cylinder  a series  of  dots  one  one-hundredth  of  a second 
apart,  furnished  the  regular  time-comparison  intervals.  Along- 
side of  this  electro-magnet  a similar  one  recorded  the  exposures. 

The  horizontal  cylinder  on  which  the  paper  was  stretched  and 
smoked  could  be  turned  by  hand  or  clock-work,  and  the  two 
magnets  were  on  a carriage,  which  travelled  slowly  from  left  to 
right  by  an  endless  screw,  as  in  the  slide-rest  of  an  engine  lathe. 

The  means  of  establishing  the  circuit  which  marks  the  openings 
or  exposures  was  as  follows : An  interrupter  disk  of  brass  and 
hard  rubber  was  fixed  on  the  axis  of  the  disks,  and  is  turned  on 
the  axle  until  the  brass  may  correspond  to  the  opening  of  the 
disks  and  there  clamped. 

A spring  with  platinum  contact  point,  and  capable  of  move- 
ment in  two  slots  at  right  angles,  is  also  adjusted  according  to  the 
number  of  openings  and  sectors  of  brass. 

The  circuit  carried  through  the  interrupter  is  taken  to  the  key- 
board that  controls  the  shutter,  and  the  pressing  the  first  key 
that  breaks  the  contact  holding  the  first  slide  allows  contact  in 
the  exposure-marking  circuit.  The  key  carries  on  a spring  a 
platinum  point  pressing  against  either  of  two  metal  strips  accord- 
ing to  its  position. 

The  inner  straight  edges  of  these  metal  strips  are  not  parallel, 
but  approach  at  one  end  ; and  the  contact  spring  being  fastened 
to  the  key-bar  by  screws  through  a slot  instead  of  holes,  the 
spring  may  be  pushed  back  and  forth  along  the  bar,  and  so  ad- 
justed that  there  is  no  appreciable  interval  between  leaving  the 
first  contact  and  gaining  the  second. 

Thus  the  counting  begins  as  soon  after  the  release  of  the  first 
shutter-slide  as  an  opening  comes  opposite  the  lens.  These  keys 
have  also  the  ordinary  adjusting-screws  of  the  telegraphic  key. 

The  pressing  of  the  second  key,  which  releases  the  second 
shutter-slide  and  stops  the  lens,  breaks  the  exposure-counting 
circuit  by  means  of  a see-saw  between  the  two  keys,  which  throws 
the  first  key  back  into  its  first  position. 


14 


THE  MECHANISM  OF 


The  exposure-counting  circuit  possesses  another  device. 

On  top  of  the  first  camera  described,  where  a peep-sight  carrying 
the  diaphragm  follows  the  movement,  are  two  parallel  strips  of 
metal  on  wooden  slides.  They  are  so  slid  past  one  another  that 
the  length  of  metal  opposite  may  equal  the  length  of  the  photo- 
graphic plate  used.  The  peep-sight  bar  carries  a bridge  clamped 
at  pleasure,  springing  its  contact  points  from  one  to  the  other 
slide,  so  that  the  circuit  passing  this  bridge  may  not  count  images 
that  might  occur  where  there  is  no  plate  to  receive  impressions. 

The  battery  used  was  composed  of  eight  Le  Clanch6  cells. 
Two,  three,  or  four  cells  in  series  are  thrown  by  a switch  into 
the  fork,  or  time-circuit. 

Two  cells  are  used  for  the  exposure-counting  circuit,  and  one 
cell  for  each  shutter-slide,  eight  in  all,  and  a ninth  cell  is  in  re- 
serve to  replace  or  reinforce  any  one  that  might  accidentally  give 
out.  The  lens  used  was  a Ross  carte-de-visite  lens  of  six  and 
three-quarter  inches  equivalent  focus.  It  is  to  be  regretted  that 
Professor  Eakins’s  admirable  work  is  not  yet  sufficiently  com- 
plete for  publication  as  a whole. 

Fig.  3. 


The  reproduction  of  a boy  jumping  horizontally,  shown  above, 
which  Professor  Eakins  has  photographed  on  a single  plate  by 


INSTANTANEOUS  PHOTOGRAPHY. 


15 


means  of  his  adaptation  of  the  Marey  wheel,  is  of  exceedingly  great 
interest,  because,  in  this  picture,  each  impression  occurred  at  exact 
intervals.  The  velocity  of  motion  can  be  determined,  by  measure- 
ment of  the  spaces  separating  the  successive  figures,  with  very  great 
precision,  as  also  the  relative  motions  of  the  various  members  of 
the  body.  The  advantages  arising  from  this  method  of  photog- 
raphy would  seem  to  render  its  further  prosecution  desirable,  as 
yielding  a means  of  measurement  as  near  scientifically  exact  and 
free  from  sources  of  error  as  we  can  hope  to  reach. 

In  1872,  Mr.  Eadweard  Muybridge,  of  California,  made  the  first 
lateral  photograph  of  a horse  trotting  at  full  speed,  for  the  pur- 
pose of  settling  a controversy  among  horsemen  as  to  “ whether  all 
the  feet  of  a horse  while  trotting  were  entirely  clear  of  the  ground” 
at  any  one  instant  of  time.  It  was  not  until  1877,  however,  that 
he  conceived  the  idea  that  animal  locomotion,  which  was  then 
attracting  considerable  attention  through  the  experiments  of  Pro- 
fessor Marey,  might  be  investigated  by  means  of  instantaneous 
photography,  with  results  of  probable  value  to  the  artist  as  well 
as  to  the  student  of  science  and  philosopher. 

Marey  had  investigated  the  action  of  a horse  by  fastening  to 
the  shoes  of  the  animal  elastic  air-chambers  which  were  con- 
nected by  means  of  flexible  tubes  to  the  pencils  of  a chrono- 
graphic  mechanism  carried  in  the  hand  of  his  rider.  At  each 
impact  of  the  horse’s  foot  with  the  ground  the  compression  of  air 
in  the  chamber  caused  the  pencil  connected  with  it  to  trace  a 
record  on  the  revolving  drum  of  the  chronograph,  and  in  this 
way  much  valuable  information  was  obtained  regarding  the  rela- 
tive action  of  the  four  feet  of  a horse  in  his  different  gaits. 

Mr.  Muybridge  proposed  to  carry  this  investigation  much  fur- 
ther by  means  of  photography.  His  plan  consisted  in  arranging 
a number  of  photographic  cameras  side  by  side  in  a line  parallel 
to  a track  over  which  an  animal  should  be  made  to  move,  so  that 
by  means  of  suitably  arranged  apparatus  an  instantaneous  photo- 
graph should  be  made  in  each  camera  of  the  series  successively, 
at  regulated  intervals  of  time  or  distance,  while  the  animal  was 
making  a complete  stride  or  cycle  of  movements  in  front  of  the 
battery  of  cameras.  The  results  would  then  show  the  animal 
in  the  several  successive  positions  which  he  assumed  in  performing 
any  particular  movement,  and  would  thus  furnish  a complete  and 


16 


THE  MECHANISM  OF 


indisputable  demonstration  of  the  disputed  problem  of  animal 
motions. 

Acting  upon  this  plan,  a few  sets  of  photographs  of  horses 
moving  at  their  various  gaits  were  taken  in  1878  with  electro- 
photographic exposors  or  shutters  devised  by  Mr.  Muybridge 
especially  for  that  work ; and  although  the  experiments  were 
made  with  wet  plates  in  the  heat  of  a California  summer,  the 
results  were  wonderfully  fine.  They  were  published  the  same 
year  by  Hon.  Leland  Standford,  under  the  title  of  “ The  Horse 
in  Motion,”  and  (together  with  others  made  in  1879)  were  ex- 
hibited by  Mr.  Muybridge  in  lectures  delivered  before  the  most 
important  scientific  and  art  societies  of  this  country,  France,  and 
England.  While  abroad  he  met  with  such  hearty  appreciation 
of  the  value  of  his  pictures,  especially  on  account  of  the  positive 
facts  which  they  gave  in  contradiction  to  many  of  the  accepted 
theories  of  animal  locomotion,  that  he  decided  to  pursue  the  sub- 
ject still  further  with  as  exhaustive  a set  of  photographic  investi- 
gations as  could  be  made  into  all  the  various  motions  of  men, 
women,  and  children,  animals  and  birds.  Moreover,  these  new 
experiments  were  to  be  made  with  new  and  greatly  improved 
apparatus  and  methods,  with  the  new  “dry  plates”  that  had  made 
possible  an  amount  of  detail  in  instantaneous  photography  un- 
attainable with  wet  plates,  and  with  the  addition  of  devices  and 
instruments  of  accuracy  for  automatically  recording  the  data  of 
each  set  of  pictures,  distance,  time,  etc.,  necessary  to  make  them 
of  practical  value  for  scientific  purposes.  Upon  the  conclusion 
of  the  investigations  the  photographic  results  were  to  be  system- 
atically arranged  and  printed  without  retouching  by  photogravure, 
and  finally  published  by  subscription  in  a manner  befitting  the 
magnitude  and  importance  of  the  work. 

After  unsuccessful  application  had  been  made  to  several  pub- 
lishers and  institutions  of  learning  for  the  necessary  means  to 
carry  out  these  plans,  the  University  of  Pennsylvania  took  the 
matter  under  its  care,  and  by  its  liberal  support  Mr.  Muybridge 
was  enabled  to  carry  on  his  work  in  the  most  thorough  manner 
to  its  completion,  with  the  gratifying  results  now  shown  in  his 
u Animal  Locomotion.” 

All  of  the  photographs  for  “Animal  Locomotion”  were  made 
in  Philadelphia, — the  birds  and  wild  animals  at  the  gardens  of 


INSTANTANEOUS  PHOTOGRAPHY. 


17 


the  Zoological  Society,  the  thoroughbred  horses  at  the  Gentle- 
men’s Driving  Park,  and  the  human  subjects,  carriage-  and 
saddle-horses,  and  other  domestic  animals  in  the  studio  at  the 
University  of  Pennsylvania.  This  out-door  studio  was  built  on 
the  grounds  surrounding  the  University  Hospital,  far  enough 
away  from  a principal  thoroughfare  to  be  undisturbed  by  pass- 
ers-by. Its  ground-plan,  diagrammed  in  Fig.  1,  was  somewhat 


Fig.  1. 


similar  in  shape  to  a semicircle.  On  the  north  side  the  diameter 
of  the  semicircle  was  a shed,  A,  B,  one  hundred  and  twenty  feet 
long,  eleven  feet  high,  and  sixteen  feet  deep,  painted  black.  The 
greater  portion  of  its  front,  D,  G,  from  the  edge  of  the  roof  to 
the  ground,  was  covered  by  a net-work  of  white  threads,  accurately 
vertical  and  horizontal,  and  five  centimetres  (almost  two  inches) 
apart,  every  tenth  thread  being  thicker  than  the  rest.  Directly 
in  front  of  this  background  ran  a level  track,  H,  J,  eight  feet 
wide,  covered  down  the  centre  with  heavy  corrugated  rubber 
matting,  K,  N.  Each  end  of  the  track  was  closed  by  a double 
gate,  O,  painted  black,  in  front  of  which  hung  an  adjustable  series 
of  vertical  threads,  H and  J,  five  centimetres  apart,  every  sixth 
thread  being  thicker  than  the  rest. 

On  the  opposite  or  southern  side  of  the  enclosure  was  the 
camera-house  R,  a long,  low  structure  with  white  front,  forming, 
as  it  were,  a chord  in  the  semicircle  of  the  fence  P,  which  ex- 
tended from  each  end  of  it  to  the  ends  of  the  track.  The  fence 
wTas  built  in  this  shape  and  slanting  outward  at  the  top,  and  the 


18 


THE  MECHANISM  OF 


inside  of  it  was  painted  white,  like  the  camera-house,  that  they 
might  reflect  light  towards  the  centre  of  the  track.  The  entire 
length  of  the  camera-house  front,  thirty-two  feet,  could  be  thrown 
open  by  a number  of  shutters  about  two  feet  wide  swinging  upward. 
Inside  the  camera-house,  and  running  almost  the  whole  length  of  it, 
was  an  immovable  table  or  counter,  on  whose  level  top  were  placed, 
side  by  side,  a battery  of  twenty-four  four  by  five  inch  cameras, 
twelve  of  which  are  represented  at  L,  with  their  lenses  at  a per- 
pendicular distance  of  about  fifteen  metres  (forty-nine  feet)  from 
the  line  of  progressive  motion  on  the  track  indicated  by  the  arrow 
I,  and  fifteen  centimetres,  or  six  inches,  apart  between  successive 
centres.  These  lenses  are  perfectly  rectilinear,  three  inches  in 
diameter  and  fifteen  inches  equivalent  focus,  and  were  ordered 
from  England  by  one  of  the  guarantors  of  the  expenditures  as- 
sumed by  the  University  of  Pennsylvania  expressly  for  these 
investigations.  In  front  of  each  camera  was  an  electro-photo- 
graphic exposor,  an  improvement  on  those  which  Mr.  Muybridge 
had  previously  invented  and  used  in  California.  A view  of  the 
camera-house,  with  the  row  of  large  exposors  inside  of  it,  is  shown 
in  Fig.  4. 

Fig.  4. 


Fig.  5 is  a diagrammatic  side  view  of  an  exposor  and  its  re- 
leasing magnet.  The  exposor  proper,  A,  is  a continuous  curtain 
of  black  rubber-cloth,  thin  but  perfectly  opaque,  moving  easily  on 
the  two  rollers  R and  R.  In  this  curtain  are  two  openings,  O and 
O,  so  placed  that  they  come  directly  opposite  each  other  in  front 
of  the  lens  L.  Motion  is  imparted  to  the  curtain  by  the  tension 


INSTANTANEOUS  PHOTOGRAPHY. 


19 


Pig.  5. 


of  stout  rubber  bands,  B,  the  duration  of  the  exposure  being 
varied  at  will  by  the  thickness  and  number  of  bands  used. 
Firmly  fastened  to  the  front  of  the  curtain  is  a wooden  pin,  C, 
to  which  are  attached  a strong  tape,  D,  with  a ring  in  the  end  of 
it,  and  another  pin,  F,  over  which  the  rubber  bands  B are  passed. 

The  releasing  magnet  consists  of  an  electro-magnet,  M,  whose 
armature  is  fastened  to  the  lower  end  of  an  arm,  I,  pivoted  at  H, 
and  having  a shoulder  on 
its  upper  end  that  may  be 
placed  over  the  extremity 
of  a three-inch  steel  lever, 

G,  and  automatically  held 
there  by  the  pressure  of  the 
band-spring  S.  The  lever 
G is  pivoted  at  a point 
about  three-sixteenths  of 
an  inch  from  its  back  end, 
in  which  is  a slight  groove 
or  indentation.  To  set  the 
exposor  previous  to  making 
a photograph,  the  front  end 
of  G is  caught  under  the 
shoulder  on  I,  the  hold 
(usually  very  slight)  being 
regulated  by  the  set-screw 
N ; the  ring  in  D is  placed 
over  the  back  end  of  G,  and 
the  rubber  bands  B are  then 
stretched  to  the  required 
tension  by  pulling  upward 
on  the  end  of  a stout  cord 
passing  under  the  pulley  P 
until  the  ring  in  the  end  of  the  cord  can  be  caught  on  a hook  in 
the  frame  of  the  exposor.  A plate  is  put  in  the  camera  and  it  is 
ready  for  action. 

At  the  proper  instant,  by  means  of  automatic  apparatus  to  be 
described  farther  on,  an  electric  current  is  sent  through  the  coils 
of  the  magnet  M ; the  armature  is  pulled  towards  it,  thereby  re- 
leasing the  lever  G,  and  the  rubber  bands,  no  longer  restrained, 


20 


THE  MECHANISM  OF 


fly  down  to  their  normal  length,  carrying  the  curtain  around 
on  its  rollers  with  great  rapidity;  the  openings  flash  past  each 
other  and  the  impression  is  made  on  the  plate.  Fig.  6 is  a front 
view  of  three  exposors,  in  the  first  of  which,  at  the  right,  the 
exposure  is  just  ending;  in  the  second  it  is  just  beginning,  while 
the  third  is  still  set.  In  this  form  of  exposor,  it  will  be  noticed, 
the  opening  or  exposure  begins,  reaches  its  maximum,  and  ends 
directly  opposite  the  centre  of  the  lens. 

Two  releasing  magnets  are 
shown  in  Fig.  7,  one  of  them 
(A)  set,  the  other  (B)  released. 

The  twenty-four  large  cam- 
eras (or  twelve,  as  the  case 
might  be),  each  with  its  sepa- 
rate exposor,  as  just  described, 
were  used  in  making  the  lat- 
eral series  of  photographs  of 
all  the  motions  investigated  at 
the  studio  excepting  the  most 
rapid  ones,  and  with  excellent 
results.  But  it  can  be  seen 
that  they  were  not  readily 
portable,  and  therefore  inade- 
quate to  do  the  work  at  the 
Zoological  Gardens  and  the 
Gentlemen’s  Driving  Park  in 
the  short  time  that  could  be 
spent  at  each  of  those  places. 
Besides  this,  it  was  desired  to 
obtain  the  different  phases  of 
a movement  not  only  in  lateral  photographs  (those  taken  from 
the  side  perpendicular  to  the  direction  of  motion,  as  in  the  Cali- 
fornia experiments),  but  from  any  point  of  view,  or  from  several 
points  of  view  at  the  same  time;  and  also  to  be  able  to  make 
changes  of  position  quickly  upon  short  notice.  These  facts 
prompted  Mr.  Muybridge  to  design  and  have  made  two  bat- 
teries of  smaller  cameras,  which  more  than  fulfilled  all  the 
requirements  of  portability  and  quick  working,  and  rendered 
possible  the  making  of  more  than  one  thousand  analytical  sets 


INSTANTANEOUS  PHOTOGRAPHY. 


21 


of  photographs  daring  the  three  months  spent  in  his  final  inves- 
tigations. 


Fig.  7. 


In  outward  appearance  each  of  these  portable  batteries  (Fig.  8) 
resembles  a rectangular  box  about  eighteen  inches  square  on  the 
ends  and  four  feet  long,  the  back  and  front  being  open,  and  the 
latter  divided  by  vertical  partitions  into  fifteen  spaces,  twelve  of 
which  are  equal.  In  each  of  the  equal  spaces  is  a releasing 
magnet  and  an  exposor  exactly  similar  in  construction  and  opera- 
tion to  the  one  described  above,  but  only  one-fourth  as  large. 


Fig.  8. 


Back  of  the  partitions,  and  resting  upon  battens  fastened  to  the 
side  of  the  box  (Fig.  9),  containing  thirteen  cameras  in  one,  for, 
though  each  of  the  thirteen  lenses  projecting  from  the  front  comes 
from  a separate  chamber,  in  construction  there  is  really  but  one 
long  bellows  ingeniously  subdivided  into  thirteen  parts.  Twelve 
of  the  lenses  pass  into  hoods  directly  back  of  the  double  open- 
ings in  the  exposors ; the  thirteenth  opens  into  one  of  the  extra 


22 


THE  MECHANISM  OF 


spaces  in  the  front,  and  by  focusing  it  all  of  the  lenses  are 
focused  simultaneously.  Three  plates,  twelve  inches  long,  fill 
the  one  plate-holder  (Fig.  9)  that  is  used  for  the  whole  battery. 
It  can  now  be  understood  that  there  is  a great  saving  of  time  in 
the  use  of  these  cameras,  due  to  the  method  of  focusing,  and  to 
having  to  fill,  empty,  and  draw  the  slide  of  only  one  plate-holder 
instead  of  twelve  for  each  series  of  photographs. 


Fig.  9. 


The  dark  room  at  the  studio  in  which  the  plate-holders  were 
filled  and  emptied  was  situated  at  the  western  end  of  the  camera- 
house,  at  V,  Fig.  1.  It  was  of  necessity  absolutely  dark,  ex- 
cepting the  few  colored  rays  which  came  through  a window  of 
ruby  glass  covered  with  dark  orange  paper;  for  the  dry  plates 
used  by  Mr.  Muybridge  were  the  most  rapid  he  could  obtain, — an 
extra-sensitive  emulsion  prepared  especially  for  him  by  Cramer, — 
and  the  slightest  premature  touch  of  white  light  would  have 
fogged  them.  The  greatest  care  was  therefore  necessary  in  han- 
dling the  plate-holders  outside.  They  were  carried  to  and  from 
the  dark  room  each  one  in  a thick  black  cloth  bag,  which  was 
removed  only  under  the  focusing-cloth  of  the  camera. 

Successive  exposures  were  made  by  sending  the  electric  current 
through  the  releasing  magnet  of  each  exposor  in  a series  succes- 
sively, at  intervals  varying  according  to  the  rapidity  of  the 
motion  photographed.  In  the  California  experiments  the  circuit 
for  each  magnet  was  usually  made  by  the  contact  of  metallic 
springs,  caused  by  the  subject  running  against  and  breaking  a 
series  of  fine  threads  stretched  perpendicularly  across  the  track  in 
front  of  each  camera.  But  this  method,  though  a very  ingenious 
one,  had  its  disadvantages  for  the  work  in  Philadelphia.  Much 


INSTANTANEOUS  PHOTOGRAPHY. 


23 


valuable  time  was  consumed  in  arranging  the  threads  for  each 
set  of  exposures;  the  time-intervals  between  successive  exposures 
were  unequal  and  unrecorded ; plates  were  frequently  wasted  by 
the  subject  making  the  exposures  prematurely,  or  when  the  char- 
acter of  his  motion  was  unsatisfactory  : and,  lastly,  such  a method 
was  impracticable  for  photographing  wild  animals  and  birds. 

To  overcome  these  difficulties,  Mr.  Muybridge  used  a circuit- 
breaker  which  he  had  devised  and  unsuccessfully  tried  in  Cali- 
fornia for  making  the  successive  electrical  contacts  automatically 
and  at  equal  intervals,  long  or  short,  as  desired.  This  was  used 
throughout  all  the  later  work.  A photograph  of  this  machine, 
which  we  shall  call  the  contact-motor,  is  reproduced  in  Fig.  10. 


Fig.  10. 


Two  vertical  standards  support  a train  of  four  multiplying 
gears,  to  which  motion  is  imparted  by  a weight  hanging  from  a 
cord  wound  on  a drum  fastened  to  the  lowest  shaft,  P.  Outside 
of  one  of  the  standards,  and  concentric  with  the  third  shaft,  is  a 
stationary  ring  or  commutator,  composed  of  twenty-four  seg- 


24 


THE  MECHANISM  OF 


ments  of  brass  separated  by  hard-rubber  insulation.  This  is 
shown  more  plainly  in  the  two  views  of  the  upper  part  of  the 
apparatus  in  Fig.  11,  and  is  represented  by  S in  the  diagram  (Fig. 
2),  to  which  future  reference  letters  will  apply.  To  each  of  the 
brass  segments  an  insulated  copper  wire  is  connected,  and  passes 
from  thence  down  through  a rubber  tube,  R,  to  the  bottom  of  the 
walnut  base  of  the  machine,  where  it  is  fastened  to  the  screw  of 
one  of  the  twenty-four  binding-posts  that  are  on  the  base  at  one 
side  of  the  apparatus.  These  can  be  seen  in  Fig.  10,  and  thirteen 
of  them  are  represented  at  P in  the  diagram.  Each  segment  and 


Fig.  11. 


each  binding-post  is  stamped  with  a number  from  1 to  24,  and 
the  wire  from  any  segment  is  connected  with  the  binding-post  of 
the  same  number. 

Loose  on  the  shaft  which  passes  through  the  centre  of  the  ring 
is  an  iron  collar  carrying  the  double  arm,  B,  outside  the  face  of 
the  ring.  The  upper  end  of  B is  bent  inward  at  a right  angle, 
and  holds  a laminated  metallic  brush  in  contact  with  the  outside 
of  the  segmented  ring,  while  a second  metallic  brush  is  held  in 
contact  with  the  iron  collar  by  a stationary  pin,  K,  projecting 
from  the  side  of  the  standard.  An  insulated  copper  wire  con- 
nected K with  a separate  binding-post,  U,  on  the  base  of  the 
machine.  From  the  lower  end  of  B a small  projection  or  nipple 


INSTANTANEOUS  PHOTOGRAPHY. 


25 


fits  into  a hole  in  a lever  fastened  to  the  armature  of  an  electro- 
magnet, M,  when  the  contact-brush  on  B rests  on  the  insulation 
between  segments  24  and  1.  (See  Fig.  11.)  The  armature- 
lever  is  held  up  by  a spring  until  drawn  away  by  the  greater 
force  of  the  electro-magnet,  when  an  electric  current  is  sent 
through  its  coils.  By  an  ingenious  mechanical  arrangement,  to 
which  we  shall  refer  more  particularly  hereafter,  when  the  arma- 
ture is  drawn  the  loose  collar  is  thrown  into  gear  with  a second 
collar  fast  to  the  shaft;  and  if  the  shaft  is  in  motion  the  brush  is 
thereby  carried  around  over  the  periphery  of  the  ring  S,  making 
contact  with  each  of  the  brass  segments  successively.  The  posi- 
tion of  the  contact-motor  in  the  camera-house  is  shown  at  M, 
Fig.  1. 

An  insulated  copper  wire  leads  from  each  of  the  twenty-four 
binding-posts,  P,  to  the  releasing  magnet  of  the  large  exposor,  L, 
of  the  same  number,  while  a second  wire  passes  from  each  of  the 
first  twelve  of  them  (P  1 to  12)  to  a double  binding-post,  D, 
stamped  with  the  same  number.  Two  cables,  G and  H,  each  over 
one  hundred  feet  long  and  composed  of  thirteen  wires,  connect  at 
one  end  to  the  double  binding-posts,  and  at  the  other  end  twelve 
of  the  wires  to  the  releasing  magnet  of  each  series  of  portable 
exposors,  F and  F,  the  thirteenth  serving  as  the  return  wire  to 
D,  B,  from  each  series  as  shown  in  the  diagram.  Another  wire 
from  D,  R,  carries  the  return  current  from  both  series  of  small 
exposors  to  a separate  binding-post,  P R,  to  which  also  a wire  with 
twenty-four  branches  conducts  the  return  current  from  the  large 
series  of  exposors. 

With  the  connections  made,  as  just  described,  a portable  battery 
of  cameras  could  be  moved  at  a moment’s  notice,  as  was  often 
necessary,  from  one  part  of  the  field  to  any  other  within  a radius 
of  one  hundred  feet  of  the  double  binding-posts;  and  at  the 
Zoological  Gardens,  on  some  few  occasions,  when  only  one  series 
of  exposures  was  desired,  the  cables  were  connected  end  to  end, 
and  then  with  the  operating  apparatus  at  one  station  the  cameras 
could  be  moved  in  any  direction  to  places  two  hundred  feet 
distant. 

The  electrical  battery,  C,  which  furnished  the  motive-power  for 
operating  the  magnets,  consisted  of  fifty-four  Le  Clanche  (prism) 
cells,  usually  arranged  in  a multiple  arc  of  three  series  of  eighteen 


26 


THE  MECHANISM  OF 


cells.  At  the  studio  they  were  placed  on  shelves  in  the  camera- 
house  at  I in  Fig  1.  A wire  from  the  negative  pole  of  the 
battery  carried  the  current  to  the  binding-post  U,  while  a wire 
from  P,  R,  carried  it  back  to  the  positive  pole.  In  the  circuit  of 
this  return  wire  the  electro-magnet  e,  m,  of  the  chronograph  was 
placed,  and  by  the  arrangement  a style  fastened  in  its  armature 
traced  a record  on  the  lampblacked  paper  covering  the  drum  J 

Fig.  2. 

mukl  LOCOMOTION. 

WAGRAMflFfLECTRICALCONNECTBNSfORMAKNGCONSECimVEf’HOTOGRAPHIC 

EXPOSURESSYNCHRONOUSLY:FROMSEVERALf>OINTSOrviEW 


whenever  the  armature  was  drawn  down  by  the  passage  of  the 
current, — simultaneously  with  the  commencement  of  each  exposure 
in  a series  of  twelve  or  twenty-four.  While  this  record  was  being 
made  a time  record  was  made  directly  under  it  by  a style  from 
the  electro-magnet  t , m,  in  circuit  with  a tuning-fork,  T.  The 
tuning-fork  used  throughout  the  investigations  was  pitched  to  one 
hundred  single  vibrations  per  second,  the  vibration  being  main- 
tained by  a separate  electric  battery  of  two  cells.  The  drum  J 


INSTANTANEOUS  PHOTOGRAPHY. 


27 


was  rotated  on  its  vertical  axis  by  clock-work,  and  could  be 
moved  up  or  down  on  the  shaft  by  means  of  a supporting  arm 
working  on  a screw,  O,  so  that  the  paper  could  be  entirely  covered 
with  records  (often  fifteen  or  twenty)  before  renewing.  The  drum 
and  shaft  were  then  lifted  out  of  the  bearings,  the  paper  cut  off, 
and  the  records  fixed  permanently  upon  it  by  immersion  in  dilute 
shellac.  The  chronograph,  its  batteries,  etc.,  were  enclosed  in  a 
wooden  box,  which  at  the  studio  stood  on  a shelf  at  C,  Fig.  1.  The 
electro-magnet  M,  whose  purpose  has  been  already  explained,  was 
operated  by  a shunt  current  from  six  cells  of  the  battery  C,  the 
circuit  being  closed  by  the  contact-key  A.  The  latter  was  de- 
signed especially  for  portability,  and  consisted  of  two  stiff  brass 
springs  with  platinum  contacts,  mounted  on  round  sticks  about 
two  feet  long,  so  that  it  could  be  conveniently  carried  in  the  hand 
from  place  to  place ; for  the  operator  usually  stood  directly  beside 
the  camera  in  which  the  first  photograph  of  the  series  was  to  be 
made,  and  by  making  the  contact  when  the  subject  reached  the 
desired  position  the  whole  series  of  exposures  was  started. 

Having  now  described  the  apparatus  in  detail,  we  can,  perhaps, 
best  understand  the  method  of  operation  by  imagining  ourselves 
in  the  studio  at  the  University,  watching  the  making  of  a series 
of  twelve  photographs  from  each  of  three  points  of  view  simul- 
taneously, thirty-six  different  negatives  in  all.  In  order  to  make 
our  observations  more  definite  we  will  suppose  that  the  action  to 
be  investigated  is  one  stride  of  a walking  horse ; that  the  large 
or  “ lateral”  cameras,  L,  Fig.  1,  are  in  their  usual  position  parallel 
to  the  line  of  motion  on  the  track  and  at  a distance  of  forty-nine 
feet  from  it;  that  the  portable  cameras,  E and  F,  have  been 
placed,  one  battery  for  front  the  other  for  “rear  sixty-degree  fore- 
shortenings,” at  a distance  of  thirty-five  feet  from  the  centre  of  the 
track;  that  is,  in  places  permanently  marked  so  that  they  point  in 
a direction  at  nearly  sixty  degrees  to  that  of  the  laterals  on  both 
sides ; the  lenses  of  all  three  batteries  are  in  the  same  horizontal 
plane  with  a certain  heavy  thread  in  the  lateral  background,  the 
“horizon  line.” 

The  cameras  being  already  focused,  an  assistant  proceeds  to  set 
the  exposors,  and  the  horse  is  started  on  a trial-trip  down  the 
track  that  we  may  see  about  how  much  time  he  occupies  in 
making  one  s stride.  We  count  ten  strides  in  eleven  seconds 


28 


THE  MECHANISM  OF 


(those  of  us  who  are  experienced  in  such  things  may,  perhaps, 
remark  that  he  is  a rather  slow  walker),  and  another  assistant 
then  adjusts  the  contact-motor  by  altering  the  weights  and  fan 
governor  so  that  the  contact-brush  will  pass  over  the  first  twelve 
segments  of  the  ring  in  about  one  and  one-quarter  seconds, 
making  a slight  allowance  for  safety ; “ because,”  the  assistant 
will  tell  us,  “we  would  rather  get  the  whole  stride  in  only  eleven 
phases  than  run  the  risk  of  not  getting  it  in  twelve,  if  the  horse 
should  decide  to  saunter  a little.”  Next  he  gets  the  chronograph 
ready  for  action,  and  the  other  assistant  meantime  having  finished 
setting  exposors,  brings  the  necessary  plate-holders  from  the  dark 
room — twelve  small  ones  for  the  lateral  cameras  and  one  large  one 
for  each  portable  battery — and  places  them  in  the  cameras.  The 
slides  are  drawn  and  we  are  all  ready. 

The  operator,  with  the  contact-key  in  his  hand,  takes  his 
stand  beside  camera  No.  1 of  the  lateral  series,  and  his  assistant 
inside  the  camera-house  starts  the  contact-motor  and  the  chrono- 
graph while  the  horse  comes  walking  down  the  track.  When  he 
reaches  a point  directly  in  front  of  camera  No.  1 the  operator 
presses  the  contact-key ; we  hear  a slight  humming  sound,  and 
thirty-six  different  photographs  of  the  horse  are  made,  three 
different  views  of  each  twelve  successive  positions  that  he  put 
himself  into  while  making  a single  stride.  If  now  we  step  in- 
side of  the  camera-house  we  can  see  on  the  drum  of  the  chrono- 
graph a record  that  was  made  simultaneously  with  the  exposure ; 
and  if  we  are  curious  to  know  we  can  count  the  number  of  vibra- 
tions in  the  lower  line  of  the  record  lying  between  the  first  and 
twelfth  drop  in  the  upper  line,  and  thus  see  exactly  how  many 
hundredths  of  a second  were  spent  in  making  the  series  of  ex- 
posures. Turning  again  to  the  diagram,  Fig.  2,  we  will  see  how 
a momentary  contact  of  the  key  brought  about  these  results. 
The  drum  of  the  chronograph,  the  tuning-fork,  and  the  shaft 
through  the  collar  of  B are  all  in  motion,  while  B is  held  in  the 
position  indicated  by  the  dotted  lines  by  a catch  in  the  armature- 
lever  of  M,  as  before  described.  In  this  position  the  brush  rests 
on  the  insulation  between  segments  24  and  1,  and  therefore  no 
circuit  for  the  electric  current.  Now  contact  is  made  for  an  in- 
stant at  the  key  A,  a current  passes  through  M,  its  momentary 
magnetic  attraction  pulls  the  armature-lever  down,  thereby  freeing 


INSTANTANEOUS  PHOTOGRAPHY. 


29 


the  arm  B and  at  the  same  time  throwing  it  into  gear  with  the 
rotating  shaft.  The  brush  is  thus  carried  around  over  the  ring  S, 
and  as  it  makes  contact  with  each  segment,  a current  passes  through 
the  three  exposor  magnets  of  the  same  number  and  through  the 
chronograph  magnet,  and  exposures  are  made  synchronously  from 
the  three  points  of  view.  With  the  brush  in  the  positions  shown 
by  full  lines  in  the  diagram  we  can  follow  the  course  of  the 
current ; from  the  negative  pole  of  the  battery  C to  the  binding- 
post  U,  thence  to  the  stationary  brush  K in  contact  with  B, 
through  B and  the  rotating  brush  to  segment  No.  2,  from  there 
through  R to  binding-post  P 2,  where  it  separates  into  two  parts, 
one  passing  through  exposor  magnet  L 2,  and  back  to  P,  R,  the 
other  to  double  binding-post  D 2,  where  it  subdivides  into  two 
parts,  passing  through  exposor  magnets  E 2,  and  F 2,  respectively, 
and  back  through  D,  R,  to  P,  R ; from  P,  R,  the  entire  current 
returns  to  the  positive  pole  of  the  battery  C,  after  passing  through 
the  chronograph  magnet  e,  m,  and  thereby  making  a record  of  that 
exposure  on  the  drum  J. 

The  way  in  which  the  contact-brush  is  automatically  thrown 
into  gear  with  the  revolving  shaft  can  be  seen  by  reference  to  the 
diagram  of  “ mechanism  for  starting  contact-brush”  (Fig.  2),  where 
some  of  the  revolving  parts  are  drawn  in  vertical  section  to  show 
the  internal  construction.  The  shaft  / is  bored  hollow  for  a part 
of  its  length,  the  internal  diameter  being  smaller  near  the  bottom 
of  the  bore  than  it  is  towards  the  end  of  the  shaft.  Into  the 
bore  fits  a spindle,  S,  whose  external  diameters  correspond  to  the 
internal  diameters  of  the  shaft.  To  the  spindle  S is  keyed  a 
collar,  O,  in  whose  outer  face  radial  teeth  are  cut.  The  key  V 
passes  through  a slot  in  the  shaft  F,  so  that  the  spindle  S,  with 
the  collar  O,  can  be  moved  in  or  out  for  a short  distance,  limited 
by  the  length  of  the  slot,  while  at  the  same  time  it  will  be  noticed 
8 and  O will  be  carried  around  with  / when  it  revolves.  Loose 
upon  / is  a second  collar,  n,  which  carries  the  double  arm  d with 
the  contact-brush,  and  has  on  its  inner  face  radial  teeth  to  gear 
into  those  in  o.  In  the  space  inside  the  shaft,  between  the  shoul- 
ders in  / and  that  in  s,  a coil  spring  is  fitted,  which  pushes  the 
spindle  outward,  throwing  o into  gear  with  n,  unless  prevented 
by  resistance  at  the  conical  extremity  of  s.  Such  resistance  is 
offered  by  the  upper  arm  of  a bent  lever,  l , whose  lower  arm  fits 


30 


THE  MECHANISM  OF 


in  a notch  in  the  extremity  of  the  armature-lever  g,  the  latter 
being  held  in  place  by  a spring.  The  double  arm  d also  catches 
in  g , as  explained  before.  Now,  with  g , l , and  d thus  arranged, 
as  shown  in  the  diagram,  let  us  suppose  /,  and  with  it  s and  o,  to 
be  revolving  at  the  desired  speed.  An  electric  current  is  sent 
for  an  instant  through  the  coils  of  the  electro- magnet  m.  Its 
consequent  magnetic  attraction  pulls  down  the  armature  c,  and 
with  it  the  lever  g.  The  spindle  s , no  longer  opposed  by  l , is 
pushed  outward  by  the  force  of  the  spring ; o is  thus  thrown  into 
gear  with  n,  and  the  contact-brush  on  the  arm  d,  now  free  to  turn, 
is  carried  around  with  the  revolving  shaft.  When  the  armature- 
lever  g is  pulled  down  as  described,  the  lower  end  of  l catches  in 
a second  notch  in  its  extremity  and  holds  it  down  until  the  motor 
is  reset  by  hand.  The  two  different  positions  of  these  levers  can 
be  seen  in  the  two  views  of  Fig.  11. 

The  most  usual  positions  in  which  two  portable  series  of 
cameras  were  placed  when  used  at  the  studio  for  making  front 
and  rear  views,  or  “foreshortenings,”  in  conjunction  with  the 
first  twelve  of  the  permanent  series  for  side  views,  or  “ laterals,” 
are  shown  in  Fig.  1,  at  / and  e,  thirty-five  feet,  at  E'  and  F', 
forty  feet,  or  at  E"  and  F/r,  sixty  feet  from  the  centre  of  the  track. 
In  the  last  two  sets  of  positions  the  cameras  pointed  directly  up  or 
down  the  track,  at  right  angles  to  the  laterals.  Photographs  made 
in  them  were  therefore  termed  “ninety-degree  foreshortenings.” 
Other  combinations  of  position  were  made  by  placing  one  of  the 
portable  batteries  of  cameras  at  sixty  degrees  front  or  rear,  with 
the  other  at  ninety  degrees  rear  or  front  respectively.  In  the 
ninety-degree  foreshortenings,  which  were  made  especially  to 
analyze  side  oscillations  of  the  body  or  limbs  during  locomotion, 
it  was  desirable  that  the  successive  points  of  view  in  the  series 
should  be  all  in  the  same  vertical  plane,  and  in  order  to  have 
them  so  the  camera-box  was  stood  on  end,  with  the  lenses  directly 
above  one  another.  When  the  cameras  were  so  placed  the  “ hori- 
zon line”  was  on  a level  with  a point  midway  between  lenses  6 
and  7,  and  the  first  exposure  of  the  series  was  made  through  the 
lowest  lens,  except  in  a few  special  cases. 

The  portable  backgrounds  used  in  all  the  photographing  away 
from  the  studio  (except  with  a few  of  the  wild  animals  at  the 
Zoological  Gardens)  were  frames  four  metres  long  by  three  metres 


INSTANTANEOUS  PHOTOGRAPHY. 


31 


wide  (approximately  thirteen  feet  by  ten  feet),  covered,  some  with 
black,  others  with  white,  cloth,  over  which  were  stretched  threads 
contrastingly  white  or  black,  forming  squares  exactly  like  those 
in  the  lateral  background  at  the  studio.  They  could  be  set  up 
and  levelled  in  a few  moments  back  of  the  course  over  which  the 
animal  or  bird  was  to  pass,  and  were  firmly  held  in  position  by 
guys. 

The  background  being  arranged  at  the  studio  or  away  from  it 
in  the  manner  described  for  each,  it  will  be  readily  understood 
that  every  photograph  in  a multiple  series  had  upon  it,  behind 
the  figure,  a number  of  equidistant  parallel  lines,  both  horizontal 
and  vertical  in  all  except  the  ninety-degree  foreshortenings  made 
at  the  studio,  where  they  were  vertical  only.  Now,  by  noting 
the  positions  of  any  part  of  the  body  upon  the  background  of 
squares  in  the  consecutive  photographs  of  a lateral  series  the 
amount  of  forward  and  upward  motion  between  successive  phases 
can  be  accurately  determined  ; and  in  the  same  way,  by  means  of 
the  background  in  the  ninety-degree  foreshortenings,  the  amount 
of  a sidewise  movement  can  be  found.  From  these  determina- 
tions the  curves  which  different  parts  of  the  body  describe  may 
be  readily  plotted.  These  trajectories,  or  those  described  by  the 
same  limbs  of  different  animals  in  performing  the  same  move- 
ments and  so  forth,  can  be  critically  compared,  and  at  the  same 
time  the  corresponding  amount  of  muscular  action  shown  in  the 
photographs  can  be  examined,  with  results  of  probably  greater 
interest  and  value  than  we  can  at  present  foretell. 

During  the  investigations  in  the  summer  of  1885  a very  inter- 
esting double  series  of  photographs  was  made  to  determine  the 
equality  of  the  intervals  between  successive  exposures,  the  accu- 
racy of  the  chronographic  record  of  these  intervals,  and  the  dura- 
tion of  the  shortest  exposures  used  in  the  work,  Mr.  Muybridge’s 
statement  that  in  some  cases  the  exposure  lasted  but  one  five-thou- 
sandth of  a second  having  been  doubted  by  several  critics.  Short 
photographic  exposures  are  usually  measured  by  photographing 
some  object  moving  rapidly  at  a known  or  readily-determined 
speed.  The  blur  in  the  photograph  shows  how  far  the  object 
moved  while  the  picture  was  being  taken,  and  from  these  data  of 
distance  and  speed  the  duration  of  the  exposure  is  calculated.  The 
usual  objects  photographed  (a  falling  ball,  a swinging  second  pen- 


32 


THE  MECHANISM  OF 


dulum,  etc.)  being  too  slow  for  such  short  exposures,  a new  method 
was  devised,  in  which  the  moving  body  was  a circular  black  disk 
over  five  feet  in  diameter,  turned  by  a crank  with  a multiplying 
gear  of  ten  to  one,  so  that  for  a single  turn  of  the  crank  there 
were  ten  revolutions  of  the  disk,  and  at  high  speed  the  chances  of 
irregularities  in  the  motion  were  therefore  reduced  to  a minimum. 
A cam  on  the  axle  of  the  disk  made  an  electrical  contact  between 
two  metallic  springs  at  each  revolution,  by  means  of  which  the 
speed  of  each  turn  was  recorded  on  the  drum  of  the  chronograph. 
On  the  black  surface  of  the  disk,  near  its  periphery,  was  a white 
spot  of  a certain  width  ; its  distance  from  the  centre,  and  (from 
that  and  the  chronograph  record)  the  distance  which  it  passed  over 
in  the  time  of  one  revolution,  were  accurately  known.  From  the 
increased  width  or  blur  of  the  spot  shown  in  each  photograph  the 
duration  of  that  exposure  was  calculated ; and  by  noticing  the 
difference  in  the  position  of  the  spot  in  any  two  consecutive  pho- 
tographs of  the  series  the  interval  between  successive  exposures 
was  determined,  it  was  seen  whether  they  were  all  equal  as  they 
should  be,  and  whether  the  intervals  determined  in  that  way  agreed 
with  those  recorded  on  the  chronograph  by  the  style  in  circuit  with 
the  contact-motor. 

In  making  the  experiment  the  two  batteries  of  small  cameras 
were  placed  side  by  side  opposite  the  disk ; they  were  arranged 
for  the  most  rapid  exposures  ever  used  in  the  investigations,  and 
the  contact-motor  was  adjusted  so  that  one  battery  should  be  dis- 
charged after  the  other,  a series  of  twenty-four  consecutive  ex- 
posures in  about  one  second.  When  all  was  ready  the  contact- 
motor  and  the  chronograph  were  started,  and  the  disk  was  re- 
volved at  a speed  of  about  two  revolutions  per  second  ; the  switch 
in  the  chronographic  circuit  of  the  disk  was  thrown  in,  and  simul- 
taneously the  contact-key  was  pressed,  and  the  series  of  expos- 
ures were  made.  A portion  of  the  very  interesting  chronographic 
record  of  the  series  is  reproduced  in  Fig.  12,  the  upper  line  re- 
cording the  revolutions  of  the  disk,  the  middle  one  in  the  vibra- 
tions of  the  tuning-fork,  and  the  lower  one  the  intervals  between 
exposures.  The  vibrations  in  the  upper  and  lower  lines,  after  the 
drop  caused  by  the  passage  of  the  current,  were  due  to  the  neces- 
sarily long  styles  in  those  two  electro-magnets,  and  are  not  so 
noticeable  in  the  regular  two-line  records  of  the  other  work. 


INSTANTANEOUS  PHOTOGRAPHY. 


33 


After  the  series  was  finished,  with  the  same  short  exposure  two 
single  photographs  were  made  : one  of  the  disk  at  rest,  in  order  to 
have  the  size  of  the  white  spot  for  comparison,  and  another  of  a 


Fig.  12. 


^lyyvvvw^ 


■^A/Vvwwww 


man  ascending  stairs,  in  order  to  show  the  amount  of  detail  ob- 
tained with  such  short  exposures.  Subsequently  all  of  these 
results  were  carefully  examined  and  worked  up  by  several  pro- 
fessors of  the  University,  whose  reports  stated  : 1st,  that  the  inter- 
vals between  successive  exposures  were  equal  except  in  two  cases, 
where  they  differed  by  a few  ten-thousandths  of  a second ; 2d, 
that  the  intervals  between  exposures  shown  by  the  photographs 
and  those  shown  by  the  chronograph  were  alike,  or,  in  other 
words,  that  the  chronograph  accurately  recorded  the  intervals  be- 
tween exposures ; and,  3d,  that  the  duration  of  the  exposure  was 
less  than  one  four-thousandth  and  more  than  one  six-thousandth  of 
a second. 

Upon  this  third  point  the  writer  cannot  wholly  agree,  but  has 
no  reason  to  doubt  that  the  effective  action  of  light  upon  the  sensi- 
tive film  was  other  than  as  stated  by  these  gentlemen. 

Such  very  short  exposures,  however,  were  only  necessary  in 
photographing  small  objects  moving  very  swiftly,  such  as  birds 
flying,  but  the  results  obtained  with  them  serve  to  show  how  great 
are  the  possibilities  of  the  application  of  instantaneous  photography 
in  the  future. 


3 


MATERIALS  FOR  A MEMOIR 


ON 

ANIMAL  LOCOMOTION. 

BY 

HARRISON  ALLEN,  M.D., 

EMERITUS  PROFESSOR  OF  PHYSIOLOGY  IN  THE  UNIVERSITY  OF  PENNSYLVANIA. 


INTRODUCTION. 

The  writer  has  undertaken,  at  the  request  of  the  representa- 
tives of  the  University  of  Pennsylvania,  a series  of  studies  on 
animal  locomotion.  The  subject  has  been  approached  from  the 
point  of  view  presented  by  instantaneous  photography,  and  has 
been  especially  based  on  the  results  obtained  by  Mr.  Eadweard 
Muybridge.  He  will  also  state  that  he  is  indebted  to  Professor 
Thomas  Eakins  for  facilities  afforded  in  studying  the  results  of  an 
experiment  in  the  use  of  a modified  form  of  Marey’s  wheel  de- 
vised by  him,  in  photographing  the  action  of  the  horse  in  motion. 

Many  of  the  statements  could  have  been  deduced  from  data 
already  accessible  to  the  writer,  but  since  he  wrote  the  paper 
immediately  after  the  inspection  of  the  photographs  his  conclu- 
sions may  be  said  to  be  based  upon  them.  At  the  same  time  he 
has  not  hesitated  to  include  materials  not  embraced  by  the  photo- 
graphs. Whenever  practicable  the  study  of  a given  series  was 
carried  on  at  the  same  time  that  the  animal  itself  lay  dissected 
before  him.  For  example,  when  studying  the  photographs  of  the 
elephant,  he  had  the  good  fortune,  through  the  courtesy  of  Pro- 
fessor Huidekoper,  to  dissect  the  limbs  of  an  elephant.  He  has 
also  dissected  the  horse,  the  ox,  the  raccoon,  the  sloth,  the  skunk, 
the  Virginian  deer,  and  the  domestic  cat.  In  the  course  of  the 

35 


36 


MATERIALS  FOR  A MEMOIR  ON 


investigation  Prof.  Horace  Jayne  extended  many  facilities.  Mr. 
Edwin  A.  Kelley  has  kindly  furnished  a carefully  prepared  list 
of  the  names  of  the  quadrupeds  and  birds;  this  appears  in  an 
appendix  to  the  report.  Mr.  Kelley  also  gave  valued  assistance 
in  the  dissections. 

To  better  inform  himself  on  the  subject  of  the  gait  of  the  horse, 
the  author  has  observed  the  impressions  made  by  the  hoofs  on  a 
sand -beach.  In  this  connection  he  desires  to  express  his  acknowl- 
edgments to  Dr.  M.  H.  Cryer  for  valuable  assistance  and  sug- 
gestions. 

The  great  delay  that  would  be  occasioned  in  the  preparation  of 
this  essay  by  subjecting  every  statement  based  upon  observation  to 
the  test  of  anatomical  demonstration,  caused  the  writer  to  remain 
content  with  making  many  of  the  conclusions  rest  upon  the  evidence 
presented  by  the  phenomena  recorded  by  the  photographs.  He  is 
aware  that  such  conclusions  are  not  in  all  respects  satisfactory. 
The  several  heads  under  which  the  appearances  are  discussed  must 
be  looked  upon  as  themes  which  suggest  research  rather  than  sum- 
maries of  work  already  done.  It  is  hoped  that  the  notes  may 
stimulate  some  of  his  readers  to  attempt  to  confirm  the  writer’s 
impressions  and  further  to  extend  the  application  which  can  be 
made  of  the  pictures  to  the  important  subject  of  animal  locomotion. 

The  “ materials”  are  so  arranged  as  to  make  two  main  groups 
of  notes, — those  pertaining  to  the  action  of  the  limb  when  on  the 
ground  and  those  pertaining  to  the  action  of  the  limb  about  to 
leave  the  ground  and  when  in  the  air.  To  these  will  be  appended 
a short  section  on  the  human  subject,  on  zoological  considerations, 
and  on  flight.  Occasional  repetitions  of  statements  of  facts  have 
been  difficult  to  avoid  in  preparing  the  notes.  The  inconvenience 
arising  from  this  defect  has  been  in  a measure  overcome  by  the 
use  of  cross-references. 

The  Use  of  Terms. 

It  is  necessary  to  propose  the  use  of  a few  terms  which  will 
clearly  express  in  a word  a meaning  which  otherwise  would  re- 
quire the  employment  of  a cumbersome  phrase.  The  words  flex- 
ion, extension,  abduction,  adduction,  pronation,  and  supination 
imperfectly  express  many  animal  movements.  Thus  no  adequate 
word  exists  for  the  movement  of  the  hand  upward  and  downward 


ANIMAL  LOCOMOTION. 


37 


when  the  forearm  is  held  in  semipronation.  Such  a motion  is  of 
importance  in  describing  the  wing  of  the  bird  and  the  bat.  The 
term  Planation  is  here  thought  to  be  convenient,  since  it  expresses 
the  fact  that  the  movement  of  the  hand  is  in  the  plane  of  the 
flexor  surface  of  the  forearm.  Planation  includes  both  pronation 
and  supination.  Contraplancition  as  easily  indicates  a movement 
at  an  angle  to  the  plane  of  the  flexor  surface  of  the  forearm.  It 
embraces  flexion  and  extension,  and  is  not  especially  demanded, 
except  that  a term  which  includes  both  flexion  and  extension  as 
well  as  abduction,  as  used  in  the  sense  of  abduction  of  the  thumb, 
may  be  acceptable. 

In  like  manner  it  has  been  found  useful  to  employ  terms  for  the 
different  orders  of  the  foot-falls. 

Synchiry  indicates  that  the  right  and  left  foot  of  a single  pair 
act  together.  Thus  in  the  canter,  gallop,  and  the  run,  the  horse 
moves  all  the  feet  synchirally.  The  movement  of  the  lower  limbs 
in  man  is  also  synchiral.  The  feet  may  act  alternately  or  together. 

In  the  strictest  sense  all  mammalian  limb-motions  are  synchiral, 
— i.e.,  the  right  and  left  parts  of  a single  pair  move  alternately. 
This  motion  is  at  its  maximum  in  the  trot,  and  at  its  minimum  in 
the  spring  as  performed  by  the  kangaroo.  The  term  is  intended 
to  apply  to  the  act  in  which  the  feet  succeed  each  other  on  the 
ground.  The  alternation  of  the  right  and  left  hind  legs  on  the 
ground,  while  the  fore  legs  are  in  the  air,  is  a posterior  synchiry; 
and  in  the  same  way  the  alternation  of  the  fore  legs  on  the  ground, 
the  hind  legs  being  in  the  air,  is  an  anterior  synchiry.  The  rabbit 
appears  to  resort  to  synchiry  as  an  alternation  of  the  walk  even  in 
the  slowest  rate  of  movement ; but,  as  a rule,  it  may  be  said  that 
synchiry  is  an  expression  of  a fast  gait. 

Asynchiry  would  naturally  embrace  the  movements  in  which 
the  feet  act  in  combinations  of  hind  and  fore  feet.  But  since  these 
movements  are  varied  and  important,  it  has  been  thought  desirable 
to  substitute  a positive  term,  and  the  word  heterochiry*  is  proposed. 
The  walk,  the  trot,  and  the  rack  are  heterochiral,  since  the  fore 
foot  is  followed,  not  by  its  fellow,  but  by  a hind  foot.  When  the 


* While  assuming  the  responsibility  for  this  word  the  writer  desires,  at  the 
same  time,  to  say  that  it  was  suggested  to  him  in  a conversation  with  his 
friend,  Professor  T.  N.  Gill. 


38 


MATERIALS  FOR  A MEMOIR  ON 


hind  foot  alternates  with  the  fore  foot  of  the  same  side  lateral 
heteroehiry  occurs.  When  with  the  fore  foot  of  one  side  the  hind 
foot  of  the  opposite  side  alternates,  diagonal  heteroehiry  takes 
place. 

In  connection  with  the  terms  flexion  and  extension  the  following 
will  be  used : The  movement  of  a limb  against  the  medium  in 
which  the  animal  is  moving  constitutes  the  stroke.  The  move- 
ment in  preparation  of  the  stroke  constitutes  the  recover . In  the 
description  of  the  “ hand-over-hand7’  movements  of  the  sloth  and 
the  ape,  the  word  “ flexion”  has  no  place ; yet  the  “ recover”  is 
used  in  as  exact  a sense  as  in  the  movements  of  any  other  animal. 

When  a limb  of  a terrestrial  quadruped  rests  upon  the  ground 
it  may  be  said  to  be  “on,”  and  when  not  on  the  ground,  to  be 
“ off.” 

The  term  sura  will  be  employed  as  a convenient  word  to  in- 
clude the  hind  limb  from  the  knee  to  the  ankle.  Crus  has  been 
retained  so  generally  as  a synonyme  for  the  entire  posterior  ex- 
tremity as  not  to  be  available. 

“ Stroke”  is  the  period  of  impact.  It  is  included  in  flexion,  and 
constitutes  its  first  stage.  “ Recover”  embraces  the  last  stage  of 
flexion  and  the  whole  of  the  period  of  “ extension.”  The  terms 
“ stroke”  and  “ recover”  are  by  no  means  the  same  as  flexion  and 
extension.  They  simply  express  certain  phases  of  limb-function 
which  are  seen  during  the  acts  of  flexion  and  extension. 

The  support  of  the  trunk  begins  in  advance  of  the  neck — viz., 
at  or  in  front  of  the  occiput  (see  p.  54) — and  passes  back  to  a 
point  midway  between  the  withers  and  the  rump.  In  the  camel 
the  fore  foot  supports  the  trunk  at  a point  as  far  back  as  the  mid- 
dle of  the  posterior  dorsal  hump.  In  the  same  animal  the  pos- 
terior extremity  supports  the  body  from  the  dorsal  concavity 
backward.  (See  p.  52.) 

In  the  Canadian  deer  (series  695,  Fig.  1)  and  in  the  fallow 
deer  (series  682  B,  Figs.  2 and  3)  the  fore  limb  at  one  stage  of  the 
gait  is  directly  under  the  trunk,  and  is  the  only  support  of  the 
body.  In  Procyon  (series  744,  Fig.  3 ; see  also  p.  72)  two  limbs 
(the  right  fore  limb  and  the  left  hind  limb)  are  in  the  same  posi- 
tion as  the  foregoing.  In  the  sloth  (series  750,  Figs.  1,  6,  7,  8,  9, 
and  12;  see  also  p.  78)  the  two  lateral  limbs  are  also  the  same. 


ANIMAL  LOCOMOTION. 


39 


The  right  hind  foot  of  the  horse  (series  631,  in  the  interval  between 
11  and  12)  is  in  the  same  attitude.  (See  p.  43.) 

Wherever  occurring  the  position  illustrates  the  tendency  for  one 
or  two  feet  of  the  same,  or  opposed  sides,  to  support  the  trunk  at 
some  point  between  the  vertical  lines  of  the  limbs.  It  is  proposed 
to  call  such  support  central.  Central  support  is  opposed  to  the 
support  of  the  limbs  in  the  extreme  or  forward  motion  of  the  fore 
limb  and  the  backward  motion  of  the  hind  limb,  which  may  be 
called  terminal. 


The  Movements  of  Limbs. 

If  a limb  can  be  conceived  moving  in  vacuo  it  can  be  at  once 
understood  that  propulsion  is  impossible.  For  propulsion  can 
follow  only  upon  the  initiation  of  an  impetus,  and  this  in  turn 
only  by  the  resistance  of  the  limb  against  the  medium  in  which 
the  animal  is  moving,  or,  in  the  case  of  the  terrestrial  animal,  the 
surface  of  the  ground. 

The  resistance  of  the  air  and  the  water  is  so  much  less  than 
that  of  the  earth  that  the  acts  of  flying  and  of  swimming  become 
radically  different  from  those  of  walking,  of  running,  or  of  any 
allied  movement.  In  flying  and  swimming  the  resistance  made 
by  the  limb  against  the  medium  in  effecting  an  impetus  does  not 
arrest  the  movement  of  the  pinion  or  the  foot;  whereas  in  terres- 
trial movements  the  instant  that  the  foot  strikes  the  earth  the 
resistance  is  great  and  the  arrest  is  complete. 

In  the  swimming-turtle  the  first  stage  of  the  recover  drives  the 
foot  in  spite  of  the  resistance  of  the  water  to  the  point  at  which 
the  second  stage  begins.  With  some  slight  modifications  the  same 
is  true  of  fossorial  animals.  Thus  in  flying,  in  swimming,  and  in 
burrowing  the  limb  describes  a continuous  movement  which  unites 
the  path  of  the  stroke  to  that  of  the  recover.  In  the  animal 
moving  on  the  surface  of  the  ground,  the  foot  being  brought  to 
rest,  an  absolute  break  occurs  between  the  beginning  of  the  act  of 
recover  and  its  completion, — the  time  which  would  be  required  to 
describe  the  interval  and  thus  to  complete  the  union  corresponds 
to  the  period  that  the  foot  is  on  the  ground. 

The  limb  rests  on  the  ground  until  the  trunk  moves  beyond 
the  point  at  which  it  can  maintain  itself.  It  is  lifted  at  intervals 
which  are  dependent  upon  the  momentum  of  the  moving  mass. 


40 


MATERIALS  FOR  A MEMOIR  ON 


One,  two,  or  three  limbs  may  be  on  the  ground  at  the  same  time. 
The  rates  at  which  the  succession  of  the  foot-falls  occur,  in  their 
turn,  depend  not  only  upon  the  rate  of  speed  at  which  the  animal 
is  moving,  but  on  the  gait  as  well.  (See  p.  59  and  infra.) 

The  Positions  of  Limbs. 

In  studying  the  motions  of  the  limb  of  a vertebrate  the  position 
which  answers  to  that  taken  by  the  salamander,  when  at  rest,  is 
assumed  to  be  the  best  adapted  for  comparison.  In  this  position 
the  limb  is  horizontal  to  the  plane  of  the  longitudinal  axis  of  the 
body.  The  ventre  of  the  body  and  the  ventral  surface  of  the  limb 
are  on  the  same  plane  nearly.  The  limb  of  a reptile  varies  scarcely 
at  all  from  that  just  named.  When  a terrestrial  animal  is  erect 
the  limb  instead  of  being  on  the  same  plane  with  that  of  the  body 
is  moved  a quarter  of  a circle  downward.  In  the  bird  the  posterior 
extremity  when  at  rest  is  in  the  same  position  as  the  terrestrial, 
but  the  anterior  extremity,  in  marked  contrast  to  it,  is  flexed. 
When  extended  the  extremity  is  thrown  upward  to  a position  as 
far  removed  from  the  horizontal  position  of  the  salamander  in  one 
direction  as  is  that  of  the  terrestrial  quadruped  in  the  other. 

In  the  movement  of  all  limbs  the  directions  in  the  main  are 
forward  and  backward.  The  forward  movement  will  be  described 
as  forward  strain , and  the  backward  movement  as  backward  strain. 
Both  the  movements  are  oblique,  but  between  them  is  a position 
which  is  straight.  In  the  terrestrial  animal  this  position  may  be 
said  to  answer  to  a line  in  the  anterior  extremity  which  lies  imme- 
diately in  advance  of  the  withers  and  in  the  posterior  extremity 
to  the  centre  of  the  acetabulum. 

THE  ACTION  OF  THE  LIMB  WHEN  ON  THE 

GROUND. 

Kinds  of  Work  done  by  the  Limbs. 

The  kinds  of  work  done  by  the  limbs  are  two  in  number, — 
viz.,  that  done  by  the  fore  limbs  and  that  done  by  the  hind  limbs. 
The  hind  limbs  are  more  powerful  than  the  fore  limbs,  and  in 
some  animals,  as  the  kangaroo  and  the  jumping-mouse,  are  the 
main  effectives.  No  terrestrial  animal  depends  for  support  upon 
the  fore  limbs.  When  all  the  limbs  are  equal,  or  nearly  equal, 
in  length,  the  preponderance  is  still  in  favor  of  the  hind  limbs, 


ANIMAL  LOCOMOTION. 


41 


owing  to  the  fact  that  the  great  backward  movement  of  these 
limbs  on  the  trunk  is  made  possible  by  the  fixation  of  the  bones 
to  the  pelvis,  and  through  this  structure  to  the  vertebral  column. 
Not  only  is  this  the  case,  but  the  hind  limbs  alone  possess  the 
power  of  propelling  the  body,  so  as  to  throw  upon  the  fore  limbs 
the  labor  of  accommodating  themselves  to  the  rate  of  work  of 
their  more  powerful  associates.  When  an  animal  is  moving  at  a 
high  rate  of  speed,  as  in  the  gallop,  the  synchiral  action  of  the 
hind  limbs  projects  the  body  with  such  force  as  to  compel  the  fore 
limbs  to,  act  simply  as  props,  which  successively  carry  the  body 
forward  until  one  of  the  hind  limbs  is  again  in  position  to  give 
the  body  a second  impetus.  In  proof  of  this  assertion  it  is  only 
necessary  to  observe  that  the  greatest  height  attained  by  the 
trunk  is  that  secured  by  the  rump  when  both  hind  feet  are  off 
the  ground.  The  statement  generally  made  that  the  horse  leaves 
the  ground  by  one  of  the  fore  feet  creates  the  impression  that  he 
gains  the  springing  force  from  this  foot,  all  the  previous  move- 
ments being  in  preparation  for  such  a spring.  In  place  of  this 
statement  another  is  here  substituted, — viz.,  that  the  horse  springs 
from  that  hind  foot  which  last  leaves  the  ground,  and  is  “ off” 
from  all  feet  when  he  simply  relinquishes  the  support  afforded  by 
the  last  prop, — that  is  to  say,  the  last  fore  foot.  (See  pp.  53,  62.) 

If  the  fore  and  hind  limbs  were  based  on  the  same  plan,  the 
motion  of  an  animal  would  be  either1  a series  of  springs — the  two 
feet  pushing  against  the  ground  at  the  same  moment — or  a series 
of  steps,  the  two  feet  moving  alternately.  While  closely  resem- 
bling one  another,  the  two  limbs  are  not  on  the  same  plan.  If 
any  motion  takes  place  in  the  vertebral  column  at  the  time  that 
the  fore  limb  is  moving,  it  is  noticed  that  it  occurs  in  the  region 
of  the  neck.  The  scapula,  has  a slight  motion  downward  and 
backward.  The  trunkal  motion  for  the  hind  limbs  occurs  in  the 
region  of  the  lumbar  vertebrae,  while  the  pelvic  bones  are  fixed. 
The  limit  of  the  forward  motion  of  the  hind  limbs  is  dependent 
upon  the  flexibility  of  the  lumbar  vertebrae.  The  limit  of  the 
similar  motion  of  the  fore  limb  is  determined  by  the  action  of  the 
muscles  alone.  The  forward  motion  of  the  fore  limbs  is  essentially 
the  same  in  all  animals,  but  the  forward  movement  of  the  hind 
limbs  is  variable,  because  the  lumbar  vertebrae  differ  in  degrees  of 
flexibility.  In  clawed  forms  there  is  more  lumbar  flexibility  than 


42 


MATERIALS  FOR  A MEMOIR  ON 


in  the  hoofed.  In  backward  movements  the  opposite  obtains,  for 
in  these  positions  the  fore  limbs  can  be  carried  back  to  a variable 
distance.  In  the  deer  and  its  congeners,  owing  to  the  great 
obliquity  of  the  humerus,  the  fore  foot  can  be  brought  to  a point 
near  the  centre  of  the  body,  and  the  limb  be  vertical.  (See  p.  92.) 
In  the  horse  the  fore  limb  in  backward  strain  is  very  oblique, 
and  the  foot,  while  well  placed  under  the  trunk,  cannot  reach  the 
centre.  In  the  baboon  the  fore  foot  cannot  pass  beyond  a verti- 
cal line  which  intersects  the  trunk  a little  back  of  the  shoulder- 
joint.  The  backward  movement  of  the  hind  limb  is  nearly  the 
same  in  all  animals.  The  leg  is  always  carried  in  a direct  path, 
the  limit  of  the  movement  being  determined  solely  by  the  length 
of  the  limb.  In  a word,  the  forward  movement  is  the  less  con- 
strained in  the  fore  limb,  while  the  backward  movement  is  the  least 
constrained  in  the  hind  limb.  The  most  variable  movements  are 
the  backward  for  the  fore  limb  and  the  forward  for  the  hind  limb. 

The  “stroke,”  or  period  of  impact  against  the  ground,  can  be 
divided  into  three  stages, — first,  that  of  forward  movement,  when 
the  foot  rests  against  the  ground,  chiefly  on  the  outer  border  (see 
p.  50) ; second,  the  vertical  position,  when  the  weight  is  borne  upon 
the  foot  as  a whole,  or  when  the  marginal  toes  are  shorter  than  the 
third  and  fourth  upon  the  central  portion  ; and,  third,  the  back- 
ward movement,  or  backward  straiu,  when  the  foot  rests  chiefly 
upon  the  inner  margin.  I am  informed  by  Dr.  M.  H.  Cryer  that 
skaters  invariably  bring  the  skate  “ on”  the  ice  by  the  outer  edge 
of  the  runner,  and  take  it  “ off”  by  the  inner  edge.  Practically 
the  same  motion  is  seen  in  swimming  for  both  hands  and  feet. 

O 

The  fore  leg  may  be  said  to  be  thrust  forward  as  the  hand  is 
thrust  when  used  for  grasping.  The  ground  may  be  said  to  be 
seized  by  the  foot  and  the  body  pulled  up  to  the  point  of  pur- 
chase. (See  p.  52.)  The  hind  leg  (usually  of  the  opposite  side) 
pushes  the  hind  part  of  the  body  forward  at  the  same  moment. 
As  the  fore  foot  passes  its  vertical  it  also  would  tend  to  push  the 
body,  and  in  this  way  assist  the  hind  leg. 

In  clawed  animals  the  seizing  power  is  carried  to  a high  state, 
and  in  hoofed  animals  it  remains  at  a low  one.  In  all  domesti- 
cated animals  the  pushing  power  of  the  hind  foot  is  unimpaired. 
(See  p.  92.)  It  is  most  modified  in  forms  adapted  for  tree  life, 
as  the  ape  and  the  sloth. 


ANIMAL  LOCOMOTION. 


43 


Motions  essentially  the  same  in  all  Quadrupeds . 

The  motions  of  all  quadruped  animals  are  essentially  the  same. 
If  a comparison  is  made  between  the  dog  and  the  raccoon,  the 
contrast  between  the  two  forms  is  at  first  sight  great.  But  if  a 
careful  analysis  of  the  figures  be  made,  it  will  at  once  be  noticed 
that  the  points  of  variance  are  in  the  main  due  to  the  rate  at 
which  the  animal  is  moving,  the  gait  being  the  same.  The  flat, 
broad,  yet  exceedingly  flexible  foot  of  the  raccoon  is  raised  delib- 
erately from  the  heel  to  the  toes,  and  at  each  stage  of  the  strain, 
which  is  coincident  with  the  heel  elevation,  the  graphic  expression 
of  the  pictures  is  totally  unlike  the  short,  decisive  motion  of  the 
small  and  almost  digitigrade  foot  as  seen  in  the  dog.  (See  p.  50.) 
But  the  order  of  the  foot-falls  is  similar  in  the  two  animals. 

In  like  manner  contrast  may  be  established  between  the  appear- 
ance of  the  foot  as  it  is  being  carried  through  the  air  in  prepara- 
tion for  a stroke.  When  an  animal  is  going  at  a high  rate  of 
speed  the  succession  of  the  movements  of  the  fore  and  the  hind 
feet  is  altered.  In  slow  rates  the  fore  foot  remains  on  the  ground 
until  the  hind  foot  is  in  its  turn  lodged.  For  an  appreciable  time 
both  feet  remain  on  the  ground  nearly  at  the  same  spot.  This 
position  is  well  seen  in  the  raccoon  (series  744,  Figs.  3 and  4)  and 
in  the  baboon,  as  well  as  in  the  sloth  (series  750).  It  affords  a 
good  example  of  central  support.  (See  p.  38.) 

But  in  fast  rates  the  fore  foot  has  left  the  ground  before  the 
hind  foot  reaches  it,  so  at  no  moment  are  the  two  feet  on  the 
ground  at  the  same  time.  Flat-footed  forms  are  capable  of  retain- 
ing the  two  feet  on  the  ground  at  the  same  time  without  the  sacri- 
fice of  speed  noted  in  the  small-footed  types,  such  as  the  soliped 
and  the  ungulate  are  compelled  to  submit  to. 

In  the  raccoon  the  fore  limb  may  be,  in  some  positions,  used  as 
a balance  to  prevent  the  animal  being  toppled  forward. 

Division  of  Parts  of  Limbs  based  upon  their  Movements. 

The  limb  is  easily  divided  into  two  great  parts, — that  from  the  hi]) 
to  the  knee  and  that  from  the  knee  to  the  toes.  The  movements 
for  the  most  part  are  the  to-and-fro  motion  of  that  portion  of  the 
hind  limb  placed  to  the  distal  side  of  the  knee,  and  to  that  part  of 
the  fore  limb  beyond  the  elbow.  The  muscles  which  move  the 


44 


MATERIALS  FOR  A MEMOIR  ON 


toes  and  the  body  of  the  foot  arise,  or  tend  to  arise,  from  the  lower 
end  of  the  femur,  while  those  which  move  the  leg  arise  from  the 
pelvis  in  great  part. 

In  ungulates  (series  682  A,  Fig.  5)  the  entire  foot  may  reach 
the  ground  when  the  animal  is  in  rapid  motion.  So  that  the 
plantigrade  expression  is  possible  in  an  animal  as  far  removed 
from  that  type  as  is  the  deer  from  the  raccoon.  The  plantigrade 
foot  is  more  flexible  than  the  digitigrade ; the  distinction  between 
the  foot  of  the  deer  and  that  of  the  raccoon  is  great,  notwithstand- 
ing the  fact  that  the  two  feet  may  under  some  circumstances  do 
the  same  work. 


Backward  Strain . 

At  the  end  of  backward  strain  of  the  hind  limb  the  fibula  will 
act  as  a check  to  eversion.  It  is  probably  one  of  the  uses  of  the 
fibula  to  thus  check  the  eversion  and  enable  the  same  bone  which 
affords  surfaces  of  origin  to  the  flexors  and  everters  to  slow  down 
the  action  excited  by  these  very  factors.  In  mammals  without 
distinct  participation  of  the  fibula  in  the  composition  of  the  ankle 
eversion  of  the  foot  is  less  pronounced  than  in  those  in  which  it 
is  present.  Thus,  in  the  raccoon,  the  fibula  enters  into  the  joint, 
and  eversion  is  evident.  In  those  instances  in  which  the  ever- 
sion is  well  developed  yet  the  fibula  is  rudimentary,  the  inversion 
of  the  knee  is  to  a corresponding  degree  emphasized. 

In  the  backward  strain,  as  seen  in  the  raccoon,  the  fifth  toe 
leaves  the  ground  before  the  fourth.  The  leg  is  always  rigid, 
but  the  extent  to  which  the  limb  lies  back  of  the  rump  varies. 
It  is  less  decided  in  the  rack  than  in  other  movements,  and  is  not 
so  well  developed  in  some  animals  as  in  others.  This  can  be 
seen  in  contrasting  the  movement  of  the  horse  and  that  of  the 
guanaco.  For  the  animal  last  named,  see  series  743. 

When  an  animal  retains  the  hind  limb  in  backward  strain  and 
the  fore  limb  in  forward  strain  (the  limbs  being  those  of  the 
same  side  of  the  body),  the  trunk  on  the  same  side  is  stretched 
out  to  the  utmost  and  the  genu-abdominal  fold  is  made  tense. 
(Series  680,  Fig.  8.)  When  the  backward  strain  of  the  hind  limb 
is  associated  with  the  backward  strain  of  the  fore  limb,  the  trunk 
is  flexed  (if  such  a term  be  permitted)  and  the  folds  just  named  are 
relaxed,  and  the  creases  of  the  skin  on  the  sides  of  the  trunk  are 


ANIMAL  LOCOMOTION. 


45 


disposed  in  a number  of  vertical  lines.  These  creases  are  espe- 
cially well  seen  in  the  skin  of  the  hog.  (Series  675.  See  p.  93.) 

It  is  a noteworthy  fact  that  the  number  and  the  position  of 
the  folds  on  the  side  of  the  hog  are  the  same  as  those  of  the  bands 
seen  on  the  side  of  the  trunk  of  the  nine-banded  armadillo,  and 
it  becomes  an  interesting  matter  for  consideration  whether  or  not 
the  bands  may  not  have  originated  in  the  same  manner,  and  for 
some  reason  remained  permanently. 

The  position  of  backward  strain,  as  already  announced,  is  most 
variable  for  the  fore  limb.  The  strain  is  not,  however,  the  same 
for  all  animals.  The  backward  inclination  of  the  humerus  is 
greatest  in  the  deer.  It  is  pronounced  in  the  other  ungulates, 
excepting  the  giraffe.  In  the  elephant  it  is  scarcely  discernible. 
(See  p.  91.) 

It  is  evident  that  the  limb  that  leaves  the  ground  the  last  is 
the  one  which  does  the  most  work.  This  function  probably  varies 
at  different  times  in  the  same  gait,  although  there  is  nothing  in 
the  photographs  which  proves  that  such  variation  occurs. 

The  amount  of  forward  strain  is  also  subject  to  variation.  The 
deer  possesses  extraordinary  power  to  throw  the  fore  limb  for- 
ward. The  degree  to  which  the  facility  to  accomplish  this  act  is 
carried  is  seen  in  series  690,  Fig.  10.  It  is  also  marked  in  the 
raccoon  (series  744,  745).  The  movement  is  much  less  marked 
in  the  horse  and  the  ungulates  generally.  The  deer  exhibits  a 
much  larger  anterior  surface  at  the  trochlear  curve  of  the  distal 
end  of  the  humerus  than  does  any  other  mammal  which  was  ex- 
amined. In  the  deer  the  proportion  is  one-sixth  of  the  shaft  of 
the  humerus,  in  the  ox  and  horse  about  one-eighth. 

The  sudden  release  of  the  backward  strain,  with  eversion  of 
the  foot,  must  naturally  tend  to  inversion  of  the  knee ; hence  a 
simple  torsion  of  the  entire  limb  is  effected.  (See  Torsion,  p.  57.) 

The  Manner  of  a Limb  going  “ off ” in  the  “ Spring.” 

The  nature  of  the  “spring”  is  not  made  clear  by  all  the  photo- 
graphs. It  is  well  seen  in  the  horse  (series  642),  but  in  the  dog 
the  immense  impetus  which  is  gained  by  the  “spring”  would  appear 
to  be  produced  by  a mechanism  altogether  inadequate  to  the  end 
in  view.  The  animal  rises  from  the  ground  without  the  source 
of  the  necessary  power  to  accomplish  this  act  being  evident.  In 


46 


MATERIALS  FOR  A MEMOIR  ON 


the  rabbit  and  the  kangaroo  it  is  easily  understood  how  by  the 
simple  extension  of  the  tarsus  from  an  acutely  flexed  position, 
followed  by  the  flexion  of  the  digits,  the  body  is  sent  upward  and 
forward  ; but  the  leg  of  the  dog  is  already  extended  at  the  time 
that  the  “spring”  is  initiated.  If,  as  is  asserted  by  practical  men, 
the  horse  is  prepared  for  the  “ spring”  by  the  same  succession  of 
foot-falls  as  in  the  gallop  or  run,  it  is  only  necessary  to  look  upon 
the  last  limb  which  leaves  the  ground  as  though  it  were  engaged  in 
preparing  the  leg  for  a recover  from  an  average  stroke.  Since  the 
eversion  of  the  foot  presses  the  inner  border  against  the  ground, 
the  inner  aspect  of  the  limb  at  the  knee  is  directed  inward  and 
subjected  to  strain.  But  the  force  generated  by  this  strain  is  un- 
expended at  the  time  that  the  foot  is  raised  from  the  ground,  so 
that  the  limb  might  be  compared  to  a coiled  spring  which  has  not 
lost  its  power,  and  the  stored -up  energy  is  engaged  to  propel  the 
body  forward  the  moment  that  the  inner  border  of  the  foot  leaves 
the  ground.  While  acknowledging  that  this  is  an  hypothesis,  it 
remains  the  best  of  the  surmises  which  occur  to  the  observer. 

It  has  already  been  seen  that  when  the  limb  is  in  the  position 
of  arrest  and  the  momentum  carries  the  body  beyond  the  perpen- 
dicular line  it  is  thrown  into  “ backward  strain.”  The  instant 
that  the  strain  begins  the  knee  is  seen  to  move  outward  and  the 
hock  to  move  inward.  The  parts  of  the  foot  below  the  heel  re- 
main unchanged.  The  impact  of  the  structures  of  the  limb  is 
thus  impaired  in  backward  strain.  It  is  well  known  that  in  the 
pentadactyle  forms  the  foot  can  be  readily  rotated  at  the  medio- 
tarsal  joint,  and  it  is  a reasonable  assumption  that  it  is  at  this  joint 
that  the  distal  part  of  the  limb  moves  when  the  entire  limb  rotates 
outward.  The  femur,  the  bones  of  the  leg,  and  the  astragalus  act 
as  one  factor,  and  the  calcaneum  and  the  remaining  bones  of  the 
foot  as  the  other  factor.  The  socket  for  the  proximal  motion 
occurs  at  the  hip,  and  that  for  the  distal  at  the  concavity  of  the 
scaphoid  bone.  There  is  also  considerable  motion  between  the 
calcaneum  and  the  cuboid  bone  and  between  the  calcaneum  and 
the  lower  end  of  the  fibula,  if  this  bone  is  present,  or  with  the 
outer  end  of  the  tibia  if  it  is  absent.  Outward  rotation  of  the 
main  portion  of  the  limb  carries  the  calcaneum  slightly  inward 
by  reason  of  the  articulation  between  the  calcaneum  and  the  bones 


ANIMAL  LOCOMOTION. 


47 


of  the  leg.  Facets  are  here  present  in  most  terrestrial  mammals. 
In  the  wombat  the  articulation  is  evident.  It  is  present  in  a 
rudimentary  form  in  man. 

The  outer  surface  of  the  calcaneum  of  the  bear  is  marked  by  a 
stout  roughened  ridge  as  it  enters  into  articulation  with  the  fibula. 
In  the  dog  the  surface  is  a small  embossment,  which  probably  is 
in  contact  with  the  fibula  only  at  the  time  of  the  backward  strain. 
In  a single  old  dog  examined  the  same  ridge  is  present  as  in  the 
bear.  A similar  ridge  which  developed  under  the  stimulus  of 
diseased  action  is  seen  in  the  skeleton  of  the  tiger  in  the  Museum 
of  the  Academy  of  Natural  Sciences  of  Philadelphia. 

As  the  knee  is  rotated  outward  the  outer  border  of  the  foot  is 
slightly  inverted.  This  disposition  is  opposed  by  the  peroneous 
longus  muscle  which  everts  the  foot.  Coincident  with  the  inver- 
sion the  external  crucial  ligament  becomes  tense  and  the  tendency 
to  torsion  is  checked. 

The  degree  of  outward  rotation  may  be  found  to  relate  to  the 
swing  of  the  trunk.  In  the  elephant  and  the  camel  the  rotation 
is  decided.  In  the  goat  it  is  apparently  absent.  It  is  less  marked 
in  the  horse  than  in  the  cat. 

The  Act  of  Turning  Round. 

In  the  dog  the  act  of  turning  is  accomplished  in  the  following 
manner : 

The  hind  feet  remaining  fixed,  the  body  moves  in  front.  It  is 
thrown  laterally  on  one  fore  limb,  so  that  this  member  becomes 
more  and  more  oblique  to  the  line  of  gravity.  At  a time  when 
a line  drawn  upward  through  the  supporting  foot  will  lie  entirely 
free  from  the  trunk  the  opposed  limb  has  been  placed  in  the  line 
of  gravity  and  a new  support  assured.  In  the  raccoon  (series  745, 
Fig.  17)  the  outer  border  of  the  foot  is  used  for  turning. 

Other  figures  which  exhibit  the  phenomenon  of  the  act  of  turn- 
ing are  those  of  the  dog,  the  horse,  the  tiger,  and  the  lion. 

On  the  Effect  of  Positions  of  the  Limbs  on  those  of  the  Head , 
the  Neck , and  the  Trunk. 

When  the  forward  movement  of  the  fore  limb  is  the  most  con- 
spicuous feature  of  the  figure  the  head  is  erect.  When  the  posi- 
tion of  backward  strain  is  the  most  conspicuous  the  head  is 


48 


MATERIALS  FOR  A MEMOIR  OX 


depressed.  When  the  head  is  being  erected  the  neck  becomes 
convex  in  front  and  concave  behind.  When  the  head  is  depressed 
the  neck  is  concave  in  front  and  convex  behind. 

The  movements  of  the  head  and  mane  can  be  satisfactorily 
studied  in  all  rapid  gaits  of  the  horse,  especially  in  the  trot  and 
the  gallop.  The  mane  flies  backward  as  the  head  descends  and 
clings  to  the  neck  as  it  ascends. 

The  series  of  figures  (649  A)  of  the  trick-horse  “ Hornet,”  rock- 
ing to  and  fro,  is  of  especial  value  in  studying  correlations  of  head 
position  to  limb  movement.  (See  p.  93.) 

The  Influence  of  the  Body  on  the  Shape  of  the  Foot. 

In  the  goat  (series  677)  the  outer  parts  are  larger  in  Figs.  10, 
11,  12,  and  the  inner  are  larger  in  Figs.  1,  2,  3,  4,  and  5. 

In  the  goat  the  chief  weight  comes  on  the  inner  toe.  In  the  doe 
(series  641)  the  two  toes  separate  at  equal  angles  to  the  axis  of  the 
leg.  In  the  ox  and  the  camel  no  difference  is  perceptible.  Profile 
views  of  the  lioness  and  of  the  elephant  are  interesting  in  this 
connection.  In  the  capybara  the  inner  border  of  the  foot  bears 
the  weight. 

Value  of  the  unequal  Lengths  of  the  Toes . 

In  a plantigrade  animal  like  the  raccoon  the  transition  from 
the  plantigrade  to  the  digitigrade  form  will  bring  the  short  toes 
to  the  ground  in  the  digitigrade  position  at  times  when  the  longer 
toes  are  yet  on  the  ground  their  entire  length.  This  position  is 
well  seen  in  series  744,  profile,  Fig.  19.  As  the  foot  passes  still 
farther  towards  the  tips  of  the  larger  toes  the  short  toes  leave  the 
ground.  At  first  they  are  in  the  axis  of  the  metapodium,  but 
afterwards  they  are  thrown  backward,  and  near  the  end  of  back- 
ward strain  appear  to  be  abducted.  (See  series  of  the  raccoon, 
744,  Figs.  9,  12,  and  13.  See  p.  73.) 

On  Obliquity  of  the  Outer  Toes. 

The  oblique  movement  will  be  essentially  the  same  in  all  in- 
stances no  matter  what  the  number  of  functionally  active  toes 
may  be.  A straight  toe  on  the  limit  of  the  inner  border  and  a 
deflected  toe  on  the  lateral  aspect  are  always  seen.  In  man  the 
first  toe  is  straight  and  all  the  others  are  inclined  outward.  In 


ANIMAL  LOCOMOTION. 


49 


the  goat,  which  has  but  two  functionally  active  toes,  the  outer  of 
the  two  is  deflected. 

The  action  of  the  toes  must  be  studied  in  connection  with  the 
outward  rotation.  It  is  evident  that  the  outward  rotation  must 
be  at  an  end,  or  near  an  end,  before  the  digits  are  taken  from  the 
ground.  (See  rotation  in  elephant,  p.  90.) 

THE  ACTION  OF  THE  LIMB  WHEN  GOING  OFF 
THE  GROUND  AND  WHEN  IN  THE  AIR. 

The  first  movement  noticed  in  the  limb  after  it  is  beyond  the 
centre  of  gravity  is  the  flexion  of  the  foot.  In  the  horse  the 
hoof  is  thrown  backward,  and  the  under  surface  of  the  foot  is 
directed  backward,  the  heel  being  raised  first.  The  sole  is  next 
directed  upward.  In  animals  possessing  more  than  one  function- 
ally active  toe  the  toes  are  quickly  adducted  in  the  air,  so  as  to 
offer  the  least  resistance  to  the  impetus  of  the  entire  body.  Asso- 
ciated with  the  above,  a pronounced  flexion  of  all  parts  of  the 
limb  occurs  excepting  at  the  hip,  where  the  movement  is  slight. 
A movement  of  the  thigh  towards  the  trunk  is  faintly  discernible. 
In  animals  possessing  long  thigh-bones,  such  as  the  elephant,  the 
movement  is  more  decided  than  in  hoofed  animals.  The  same 
remarks  are  applicable  to  the  movements  of  the  humerus.  The 
degree  to  which  flexion  is  carried  is  more  marked  in  the  young 
than  in  the  adult,  and  in  terrestrial  than  in  arboreal  creatures.  In 
the  sloth  ( Choloepus ) flexion  is  absent,  the  limbs  being  advanced 
by  a swinging  motion  at  the  shoulder  and  the  hip.  (Fig.  11,  p.  83.) 
In  rapid  gaits  the  unaided  eye  receives  the  impression  of  backward 
movement,  but  fails  to  be  impressed  with  forward  movement.  It 
may  hence  be  inferred  that  the  former  is  a quicker  movement 
than  the  latter. 

In  the  fore  limb  the  last  state  of  extension  of  the  forearm 
answers  to  the  action  of  the  extensors  of  the  carpus  and  of  the 
digits.  In  the  less  delicate  movements  of  the  hind  limb  the 
muscles  which  extend  the  tarsus  and  the  toes  move  the  foot  with 
less  precision,  and,  it  is  likely,  with  less  speed.  The  first  stage  of 
the  recover  is  a deliberate  act.  Beginning  at  the  toes,  it  ends  at 
the  hip.  The  second  stage  is  quicker  than  the  preceding  and  is 
more  abrupt.  Beginning  at  the  hip,  it  ends  at  the  toes. 

4 


50 


MATERIALS  FOR  A MEMOIR  ON 


Proposition  that  the  Foot  strikes  the  Ground  by  the  Outer  Border. 

This  movement  most  probably  takes  place  in  a constant  manner 
in  all  quadrupeds.  Huxley*  describes  the  act  in  the  chimpanzee 
as  though  it  were  peculiar  to  that  animal.  In  the  horse  the 
movement  is  well  seen  in  series  601,  Figs.  3 and  4,  left  hind  foot. 
It  is  also  seen  in  Fig.  4 of  the  right  foot  of  the  same  series.  The 
action  is  well  seen  in  series  581,  Figs.  10  and  11.  (See  pp.  42,84, 88.) 

The  foot  in  all  animals  excepting  the  horse  (and  even  in  this 
single-toed  form  the  movement  of  the  foot  is  in  nearly  all  essen- 
tials the  same)  is  carried  forward  in  semi  pronation.  After  the 
foot  strikes  the  ground  on  the  outer  border  pronation  begins,  and 
is  completed  by  the  time  the  perpendicular  line  is  reached.  The 
foot  leaves  the  ground  by  the  inner  border  (the  toes  being  succes- 
sively abducted),  so  that  the  pressure  of  the  body  is  borne  from 
without  inward  across  the  foot.  (See  Fig.  4,  p.  73.)  The  foot 
is  always  everted  as  it  leaves  the  ground.  In  a plantigrade  animal, 
as  the  raccoon,  the  foot  is  carried  during  the  last  part  of  recover 
nearly  parallel  to  the  plane  of  support.  In  the  rapid  motion  of 
ungulates  and  of  the  horse  the  foot  may  actually  touch  the  ground 
nearly  to  the  hock.  (See  p.  43.)  In  backward  strain  the  hock  or 
heel  is  gradually  raised,  and  at  the  end  of  strain  the  animal  is 
seen  touching  the  ground  by  the  tip  of  the  inner  functionally  active 
toe.  In  the  horse  the  foot  leaves  by  the  tip  of  the  hoof.  It  is 
likely  that  the  degree  of  impact  of  the  outer  border  of  the  foot 
will  be  found  to  correlate  with  the  degree  of  development  of  the 
calcaneo-sural  joint, f since  the  weight  must  be  carried  along  the 
outer  border  to  the  rest  of  the  limb.  At  the  end  of  backward 
strain  the  limb  from  the  knee  distally  is  in  the  same  line. 

The  entire  series  of  changes  from  semipronation  to  pronation, 
as  studied  in  connection  with  the  transfer  of  weight  across  the 
foot,  is  well  seen  in  the  tiger  (series  729  and  730;  see  also  p.  85). 

The  Evasion  of  the  Foot. 

The  moment  flexion  begins  eversion  is  established,  and  the  limb 
becomes  angulated  outward  at  the  ankle.  The  main  axis  of  the 
proximal  facet  of  the  astragalus  is  correlative  with  the  degree  of 

* Medical  Times  and  Gazette , April,  1864,  898. 

f A name  proposed  for  the  joint  existing  between  the  fibular  process  of  the 
calcaneum  and  the  fibula,  or  the  tibia. 


ANIMAL  LOCOMOTION. 


51 


this  obliquity.  The  angulation  is  most  pronounced  in  the  horse, 
less  so  in  the  ox,  and  scarcely,  if  at  all,  in  the  hog.  (See  p.  55.) 

It  is  evident  that  the  more  the  toes  are  separated  the  better  the 
limb  is  supported.  It  would  appear  to  be  one  of  the  uses  of  the 
digits  that  they  are  capable  of  moving  so  as  to  increase  the  width 
of  the  under  surface  of  the  foot.  Such  an  increase  of  width  en- 
sues from  two  causes, — first,  from  the  pressure  outward  of  the 
foot  against  the  ground ; and,  second,  from  the  traction  of  the 
digits  by  the  action  of  muscles.  The  muscular  action  is  most 
pronounced.  It  is  well  defined  along  the  outer  border  of  the 
foot.  As  the  pressure  shifts  across  the  foot  from  the  outer  to 
the  inner  border,  the  digits  leave  the  ground  and  are  lifted  and 
abducted  as  they  are  relieved  from  duty.  In  the  capybara  the 
movement  of  abduction  begins  before  the  limb  reaches  the  ground 
(series  746,  Fig.  6).  Just  as  the  foot  is  lifted  the  inner  border  is 
turned  outward  and  the  sole  is  disposed  to  the  air  in  the  position 
of  eversion, — that  is  to  say,  the  sole,  while  directed  outward,  is 
so  arranged  that  the  inner  border  of  the  foot  is  directed  down- 
ward and  the  outer  border  upward.  As  the  foot  is  everted  the 
toes  become  abducted. 

Eversion  is  well  seen  in  the  horse  (series  622  and  633).  It  is  pres- 
ent, but  less  marked,  in  the  deer  (series  681).  A good  study  can  be 
seen  in  series  619.  In  the  slow  movement  of  the  walk  the  feet  are 
not  everted  at  the  moment  of  the  removal  of  the  weight,  but  after 
the  feet  are  well  in  the  air.  This  is  especially  noted  in  series  581. 

In  series  594  the  figures  of  foreshortening  show  that  when,  as 
in  Figs.  3 and  6,  the  fore  foot  is  lifted,  the  foot  moves  towards  the 
median  line,  and  when  the  hind  limb  moves  it  swings  off  from  the 
trunk.  It  is  likely  that  the  greater  width  of  the  pelvis  over  that  of 
the  withers  compels  the  hind  limb  to  describe  an  excursus  outward. 

That  the  amount  of  motion  inward  under  the  body  is  suscep- 
tible of  modification  is  evident  from  the  fact  that  among  fast 
pacing-horses  the  feet  are  brought  inward,  in  order  to  reach  the 
same  spot  on  the  ground.  Since  the  fore  limb  is  the  more  mobile 
of  the  two,  it  is  likely  that  in  the  process  of  adaptation*  the  in- 


* The  word  “ adaptation”  is  here  used  in  the  sense  that  a terrestrial  animal 
possesses  the  power  of  modifying  to  a slight  degree  the  movements  of  the 
limbs  according  to  the  character  of  the  ground  it  is  moving  upon.  (See  p.  96.) 


52 


MATERIALS  FOR  A MEMOIR  ON 


ward  movement  is  secured  by  the  front  limbs,  and  that  the  hind 
limbs  remain  the  same.  (See  p.  42.) 

In  the  sloth  the  foot  is  lifted  as  well  as  swung.  (See  Fig.  11, 
p.  83.)  It  would  be  interesting  to  ascertain  if  the  ape  also  lifts 
the  limbs  in  swinging. 

All  elements  of  the  swing  of  the  hind  limb  appear  to  be  lost 
in  the  “jump”  if  the  two  hind  feet  act  synchronously. 

In  the  camel  the  fore  foot  in  backward  strain  answers  to  a ver- 
tical line  which  intersects  a point  as  far  back  as  the  middle  of  the 
posterior  dorsal  hump,  while  the  hind  limb  advances  forward  as 
far  as  the  concavity  between  the  humps.  (See  p.  38.) 

The  Degrees  made  by  the  Limbs  at  the  Extremes  of  Forward  and 
Backward  Movement . 

The  fore  limb  when  at  the  extreme  of  forward  movement  pre- 
sents an  axis  which  is  very  oblique  as  compared  to  the  limb  when 
in  the  perpendicular  position.  Again,  when  in  the  extreme  of 
backward  movement  it  is  again  oblique  to  the  same  perpendicular 
position.  It  has  been  thought  of  sufficient  interest  to  record  the 
exact  degrees  presented  by  these  extremes  of  movement  in  the 
fore  limb  and  to  contrast  them  with  similar  movements  of  the 
hind  limb. 

By  the  use  of  the  word  plus,  or  the  plus  sign  (+),  a deviation 
to  the  right  of  the  vertical  is  indicated.  In  like  manner  minus, 
or  a minus  sign  ( — ),  indicates  a deviation  to  the  left. 

In  the  elephant  (series  733,  Fig.  13)  the  forward  strain  of  the 
fore  limb  is  25°  minus.  The  backward  strain  is  35°  plus.  In  the 
hind  limb  (Fig.  10)  the  forward  strain  is  15°  plus  and  the  hind 
strain  (Fig.  9)  is  45°  minus.  In  the  lioness  (series  728,  Fig.  3)  the 
forward  strain  is  50°  and  the  backward  strain  20°.  In  the  hind 
leg  the  forward  strain  is  50°  and  the  backward  strain  50°. 

In  the  dog  (series  707,  Fig.  1)  the  fore  foot  at  the  end  of  back-  . 
ward  strain,  but  as  yet  on  the  ground,  is  in  an  axis  of  10°  minus; 
the  rest  of  the  limb  being  20°  plus  nearly.  In  Fig.  2,  the  foot 
having  left  the  ground,  marks  80°  minus,  nearly,  while  the  rest 
of  the  limb  remains  nearly  the  same  as  when  on  the  ground, — 
namely,  18°  plus.  In  the  hind  leg,  as  in  Fig.  5,  the  foot  when 
at  the  end  of  backward  strain  gives  an  axis  of  90°  minus ; while 
that  of  the  metatarsus  gives  10°  minus ; and  that  of  the  thigh  is 


ANIMAL  LOCOMOTION. 


53 


less  than  5°  from  the  vertical.  In  Fig.  6,  the  foot  has  left  the 
ground,  and  with  the  metatarsus  and  leg  to  the  knee,  become 
deflected  to  40°  minus,  while  the  thigh  remains  the  same, — 
namely,  less  than  5°  plus.  In  series  690  (Cervus  dama,  fallow 
deer)  the  anterior  oblique  is  140°,  and  the  posterior  10°. 

The  method  here  accepted  of  determining  the  degrees  of  the 
deflection  of  the  different  parts  of  the  limb  is  sufficiently  accurate 
for  all  purposes  except  in  the  case  of  the  thigh,  where  the  slight 
movement  of  the  entire  mass  forward  is  an  imperfect  index  to  the 
deflections  of  the  femur. 

It  will  be  seen  that  the  fore  limb  moves  as  a whole,  while  the 
hind  limb  varies  in  each  of  its  segments.  It  is  true  the  fore  limb 
presents  an  angulation  between  the  axes  of  the  digits  in  hoofed 
animals  and  the  rest  of  the  limb,  but  on  the  whole  the  limb  may 
be  compared  to  a prop.  (See  pp.  41,  62.) 

In  a general  way  it  may  be  said  that  the  forward  strain  of  the 
fore  limb  is  parallel  in  the  lioness  to  the  forward  strain  of  the 
hind  limb;  but  the  deflection  of  the  hind  limb  in  forward  strain 
is  two  and  one-half  times  greater,  as  compared  with  that  of  the 
fore.  In  the  elephant  the  forward  strain  of  the  fore  limb  is 
greater  than  the  forward  strain  of  the  hind  limb  by  ten  degrees ; 
and  the  backward  strain  of  the  fore  limb  is  ten  degrees  less  than 
that  of  the  hind.  The  general  trend,  therefore,  of  the  two  limbs 
in  animals  so  remote  as  the  tiger  and  the  elephant  presents  con- 
trasts which  in  their  way  are  as  great  as  the  anatomical  peculiari- 
ties of  the  animals  themselves. 

The  correlations  of  these  deflections  with  the  trunk  are  doubt- 
less exact,  but  no  systematic  effort  has  been  made  to  define  them. 
A vertical  line  drawn  upward  through  the  foot  and  made  to  in- 
tersect the  vertebral  column  might  be  made  available  in  the  for- 
mation of  an  index  of  importance.  It  is  noticed  that  in  the 
photograph  of  the  lioness  this  vertical  line  corresponds  to  the 
second  of  the  minute  dorsal  elevations.  As  a general  rule,  it  may 
be  said  that  the  line  intersects  the  vertebral  column  at  a point 
answering  to  a distance  of  twice  the  breadth  of  the  withers.  Again, 
in  the  lioness  the  forward  strain  of  the  hind  foot  yields  a point  by 
wThich  the  vertical  line  can  be  drawn  upward  which  intersects  the 
vertebral  column  at  the  last  of  the  dorsal  marks. 

While  the  purpose  of  the  forward  strain  in  the  claw-footed 


54 


MATERIALS  FOR  A MEMOIR  ON 


animals  is  to  secure  a purchase  on  the  ground  by  which  the  trunk 
can  be  pulled  forward,  in  the  hoofed  animals  it  exhibits  another, 
— namely,  to  protect  the  massive  head.  (See  succeeding  section.) 


The  following  measurements  have  been  made  of  the  hind  limb 
of  the  horse  at  end  of  backward  strain  in  the  rack,  the  pace,  the 
trot,  and  the  gallop  : 


Rack. 

590,  Fig.  2 
Foot,  2°+ 
Metat.,  8°-f- 
Leg,  40°+ 


Pace. 

591,  Fig.  9 
Foot,  0° 
Metat.,  21°-j- 
Leg,  50° -f 


Trot. 

Time,  17. 
607,  Fig.  16 
Foot,  0° 
Metat.,  21°-f- 
L eg,  4ft°+ 


Trot. 

Time,  19. 

609,  Fig.  2 
Foot,  1°+ 
Metat.,  30°  4- 
L eg,  40°+ 


Gallop. 

631,  Fig.  3 
Foot,  0° 
Metat.,  40° -f- 
Leg,  60°-f- 


Extent  of  Forward  Movement  of  the  Anterior  Extremity . 

The  position  of  the  hoof  of  the  fore  foot  in  forward  strain 
varies  with  respect  to  the  head  in  different  ungulates.  In  the 
heavily-built  forms,  as  the  ox,  it  reaches  the  occiput  only,  in  the 
Indian  buffalo  (series  701)  the  ear,  while  in  the  deer  (series  688) 
it  appears  to  advance  even  beyond  the  muzzle.  , (See  p.  38.) 

This  arrangement  doubtless  correlates  with  the  massiveness  of 
the  head,  when  the  fore  limb  comes  to  the  rest  beneath  the  head, 
as  in  the  Indian  buffalo  and  allied  animals,  and  with  speed,  when 
it  reaches  the  ground  in  advance  of  the  centre  of  the  head. 

The  extreme  position  of  the  hind  limb  after  it  is  taken  off 
varies  greatly,  as  indeed  it  also  does  in  the  limb  just  prior  to  its 
being  lifted  from  the  ground. 

The  changes  in  the  relative  positions  of  the  fore  foot  when  off 
in  the  various  gaits  are  important.  In  the  dog  and  the  doe  the 
entire  extremity  is  acutely  flexed.  In  the  adult  deer  it  is  ex- 
tended, as  is  also  the  case  in  the  cat.  (See  p.  92.) 

The  hind  foot  appears  to  retain  its  position  for  a longer  time 
than  the  fore  foot, — that  is  to  say,  in  the  fore  limb  the  impres- 
sion is  given  that  it  is  preparing  to  leave  the  ground  soon  after  it 
passes  its  vertical,  while  in  the  hind  limb  the  propulsive  power 
is  expended  through  the  entire  period  of  the  “ stroke,”  and  is 
as  pronounced  in  the  positions  back  of  the  vertical  as  in  any 
other. 

The  toes  of  the  fore  leg  are  flexed  quickly,  even  in  Echidna 


ANIMAL  LOCOMOTION. 


55 


and  Solenodon.  So  far  as  observed,  all  mammals  flex  the  toes  of 
the  fore  leg  not  only  quicker  than  the  hind,  but  more  completely. 

The  adduction  of  the  toes  after  the  removal  of  the  weight  of 
the  body  does  not  appear  to  be  the  result  of  a mechanical  neces- 
sity, for  it  is  subject  to  variation.  It  is  less  prompt  in  the  fore 
limb  than  in  the  hind.  At  times  when  the  hind  foot  is  raised  it 
tends  to  be  abducted.  An  example  of  such  retention  is  seen  in 
series  594,  Fig.  5. 

“ Slowing  Up.” 

The  descent  of  the  limb  must  have  an  appreciable  effect  on  the 
momentum  of  the  body  by  presenting  a surface  of  resistance  to 
the  air.  This  occurs  in  the  manner  made  familiar  by  the  bird  in 
the  act  of  depressing  the  tail-feathers  to  arrest  flight.  Great 
breadth  of  limb  is  therefore  an  unfavorable  condition  for  rapid 
locomotion.  The  figures  of  a cat  jumping,  as  seen  in  series  719, 
Figs.  1,  14,  and  15,  serve  to  illustrate  the  action. 

Position  of  Feet  in  the  Last  Stage  of  Recover. 

The  feet  in  forward  motion  are  carried  in  the  position  of  semi- 
pronation during  the  first  stage  of  the  movement.  This  act  is 
the  best  adapted  to  rapid  action,  since  it  presents  the  smallest 
surface  of  the  limb  to  the  resisting  air.  (See  p.  49.) 

The  Angulation  of  the  Limb  at  the  Ankle  due  to  Direction  of  the 
Trochlear  Axis  of  the  Astragalus.  (See  p.  50.) 

Among  the  more  pronounced  correlations  which  exist  between 
the  contour  of  the  limb  and  the  deeper  structures  is  the  shape  of 
the  ankle.  This  is  seen  in  the  horse,  the  ox,  and  the  hog.  If  the 
astragalus  of  each  of  these  animals  is  examined,  it  will  be  found 
that  the  deflection  of  a line  drawn  through  the  upper  or  pulley 
surface  forms  an  angle  with  the  axis  of  the  limb  of  varying 
degrees  in  the  horse  and  in  the  ox,  but  none  in  the  hog.  The 
production  of  such  a line  in  the  limb  whose  leg-  and  foot-bones 
are  in  the  positions  assumed  in  life  will  show  that  the  produced 
line  of  the  surface  in  the  horse  intersects  the  metatarsus  twenty 
centimetres  below  the  proximal  end  of  the  bone,  in  the  ox  at 
eleven  centimetres,  and  in  the  hog  the  axis  is  parallel  with  the 
tarsus. 


56 


MATERIALS  FOR  A MEMOIR  ON 


With  these  facts  before  us  and  the  photographs  examined,  it 
will  be  seen  that  in  the  horse  (series  576),  the  figure  of  the  animal 
being  seen  foreshortened  from  behind  at  ninety  degrees,  the  right 
hind  foot  is  barely  off  the  ground,  and  has  not  lost  the  position 
of  the  ankle  when  seen  in  backward  strain.  The  produced  axis 
of  the  leg  will  intersect  the  axis  of  the  metatarsus  at  the  position 
which  corresponds  to  the  production  of  the  axis  of  the  astragalus- 
pulley  in  the  skeleton. 

In  the  ox  (series  671,  Fig.  12)  the  rear  view  of  the  left  hind 
leg  exhibits  a totally  different  inclination.  The  foot  is  on  the 
ground,  but  is  about  to  leave  it,  and  the  produced  line  is  much 
nearer  the  vertical.  In  the  hog,  as  shown  in  series  674,  Fig.  4, 
the  axis  of  the  astragalus  as  far  as  can  be  ascertained  is  also  that 
of  the  leg. 

Training  and  Age  as  Factors  of  Disturbance. 

The  difficulty  in  studying  the  actions  of  the  domesticated  ani- 
mals, especially  of  the  horse,  is  owing  in  the  main  to  the  fact 
that  the  training  to  which  the  animal  has  been  subjected  modifies 
his  movement.  The  draught-horse  comes  down  on  the  tip  of 
the  foot  instead  of  the  heel,  as  is  the  case  with  other  quadrupeds. 
In  like  manner  the  movements  of  the  well-bred  horse  are  influ- 
enced by  the  skill  of  the  driver.  In  the  gallop  (series  624)  it  is 
evident  that  the  rider  is  at  fault  in  the  management  of  the  horse 
and  disturbs  his  action. 

The  trot  and  the  fast  gaits,  such  as  the  run  and  the  act  of  the 
leap  as  taken  by  the  horse  trained  for  the  circus,  are  unnatural, 
and  belong  to  the  class  of  the  acts  of  the  acrobat  and  the  contor- 
tionist as  seen  in  the  human  movements.  (See  p.  66.) 

The  fact  that  the  horse  in  racing  can  place  each  of  the  feet  in 
succession  in  the  same  spot  is  in  this  relation  unessential,  and  need 
not  militate  against  any  conclusion  drawn  from  slower  and  more 
natural  movements.  The  same  remark  is  applicable  to  the  fact 
that  the  fast  horse,  even  in  the  walk,  will  place  the  hind  foot  on 
the  ground  in  advance  of  the  fore  foot. 

The  age  of  an  animal  will  modify  the  movements.  An  old 
horse,  as  already  seen,  will  place  the  tip  of  the  hoof  to  the  ground 
instead  of  the  heel.  In  the  same  class  the  hind  foot  is  advanced 
to  a less  degree  than  the  young.  In  the  colt,  on  the  other  hand, 


ANIMAL  LOCOMOTION. 


57 


the  forward  strain  is  the  greater.  In  the  fawn,  as  already  re- 
marked, the  feet  are  more  flexed  than  in  the  adult  deer.  An 
untrained  adult  feral  animal  is,  all  things  remaining  the  same, 
the  best  form  which  should  be  taken  for  study. 

The  weight  of  the  rider  being  thrown  forward  on  the  fore  legs 
may  modify  the  gait.  That  the  depression  of  the  head  in  the 
forward  movement  of  the  legs  is  not  dependent  upon  this  circum- 
stance is  shown  in  the  figures  of  the  rocking  horse  (series  649  A). 
An  additional  reason  is  here  presented  why,  when  practicable,  a 
form  taken  for  study  should  be  feral.  (See  also  remarks  on  the 
trot,  p.  66.) 

Torsion  of  the  Trunk. 

An  animal  in  thrusting  out  a limb  from  the  body  may  be  com- 
pared to  a boxer  making  a thrust  with  his  arm.  With  each  lunge 
the  body  is  turned  in  the  direction  in  which  the  lunge  is  made,  and 
the  impetus  of  the  body-movement  is  added  to  the  force  of  the 
blow.  The  twist  that  the  body  describes  is  checked  by  the  plant- 
ing down  of  one  of  the  disengaged  feet. 

In  the  dog  (series  707),  while  both  hind  limbs  are  off  the  ground 
and  the  body  is  being  vaulted  on  the  single  fore  limb,  the  entire 
posterior  part  of  the  body  is  deflected  from  the  line  of  the  main 
axis  of  the  vertebral  column.  This  motion  is  certainly  dependent 
on  the  bending  of  the  column,  and  is  probably  an  example  of 
torsion.  If  unchecked  the  motion  would  “ twirl”  the  body  round 
on  itself. 

But  since  the  impression  of  the  foot  on  the  ground  remains 
sharply  outlined,  it  is  probable  that  the  “twirl”  is  greater  in  the 
proximal  than  in  the  distal  joints,  and  is  entirely  lost  by  the  time 
that  the  parts  of  the  limb  are  reached  which  rest  upon  the  ground. 
Thus  the  first  impetus  towards  deflection,  while  originating  in  the 
vertebral  column,  is  gradually  transferred  to  that  limb  which  at 
the  time  is  serving  as  a prop,  and  the  force  of  the  movement  is 
dissipated  as  the  animal  is  carried  forward. 

In  animals  possessing  a rigid  vertebral  column  the  torsion 
which  corresponds  to  the  movement  above  described  is  not 
marked.  But  the  disposition  of  the  body  to  incline  towards  the 
side  which  perfects  the  forward  strain — i.e.,  delivers  the  blow — is 
the  same.  Such  inclination  if  unchecked  would  throw  the  body 


58 


MATERIALS  FOR  A MEMOIR  ON 


off  the  straight  line.  The  check  is  secured  by  the  hind  foot  of 
the  opposed  side  of  the  trunk  coming  on  the  ground. 

Series  707,  Fig.  6,  shows  to  advantage  the  disposition  exhibited 
by  the  dog  to  twist  the  trunk  during  progression.  This  tendency 
is  never  seen  in  the  finer  varieties  of  the  animal. 

The  Act  of  Kicking. 

In  series  658,  which  exhibits  the  kick  of  the  horse,  Fig.  1 shows 
the  hind  foot  as  not  quite  extended.  When  the  kick  is  complete 
the  foot  is  fully  extended,  as  seen  in  Fig.  2 of  the  same  series. 

The  Position  of  the  Fore  Limb  as  to  the  Axis  of  the  Trunk . 

An  inclination  exists  for  the  foot  to  rest  on  the  ground  directly 
in  the  middle  line  of  the  body ; but  the  foot  is  not  brought  to  the 
ground  in  this  position,  but  to  the  opposed  side, — that  is  to  say,  it 
crosses  the  median  line,  and  comes  down  on  the  right  side  of  the 
line  if  the  left  foot  is  considered,  and  to  the  left  if  the  right  side 
is  considered.  Such  disposition  is  seen  in  the  photographs  of  the 
dog  (series  703,  Fig.  2,  and  series  704,  Figs.  5 and  6).  The  mo- 
tion described  is  best  seen  in  the  heavy  type  of  animal.  It  disap- 
pears in  the  slender  breeds,  as  the  greyhound.  The  same  remark 
is  applicable  to  the  horse,  the  crossing  of  the  fore  legs  being  seen 
only  in  the  heavy  breeds. 

The  foot  which  comes  to  the  ground  at  the  median  line  will 
gradually  be  drawn  to  the  lateral  portion  of  the  trunk,  as  seen  in 
series  709,  Figs.  4 and  5.  In  this  position  it  leaves  the  ground. 
The  prop  movement  must  from  this  circumstance  be  less  efficient 
towards  the  end  of  the  vault  than  it  was  at  the  beginning. 

The  crossing  of  the  fore  legs  is  admirably  well  seen  in  same 
series. 

Depression  of  the  Heel. 

Complete  forward  movement  of  the  limb  tends  to  depress  the 
heel,  or,  per  contra , the  forward  movement  of  each  extremity 
tends  to  draw  the  toes  away  from  the  plane  on  which  they  are  to 
fall  (series  601,  trotting-horse). 

Inward  Potation. 

After  the  hind  leg  leaves  the  ground  the  limb  is  disposed  to 
rotate  inward,  an  act  well  seen  in  the  horse  and  the  elephant 


ANIMAL  LOCOMOTION. 


59 


(Fig.  1).  The  ilio-psoas  would  have  an  apparent  effect  in  prevent- 
ing this.  It  may  be  surmised  that  this  muscle  is  a check  to  the  ex- 
cessive inward  rotation,  or  the  muscle  may  not  contract  until  later, 
and  prove  to  be  the  chief  factor  in  the  second  stage  of  the  recover. 
(See  p.  89.) 

Fig.  1. 


The  figure  is  designed  to  illustrate  the  disposition  for  the  limb  to  rotate  inward.  The  inner  border 
of  the  uplifted  foot  is  oblique,  and  the  leg  is  inclined  towards  the  median  line  of  the  body. 


THE  GAIT,  OR  THE  SUCCESSIONS  OF  FOOT-FALLS. 

The  order  in  which  the  feet  comes  to  the  ground  would  be  a 
simple  matter  for  study  if  the  animal  moved  constantly  at  a given 
speed  and  gait.  It  is  rational  to  assume  that  the  movements  are 
in.  part  automatic,  and  the  alternate  motions  of  the  right  and  left 
limbs,  or  the  motions  of  both  the  left  limbs  alternately  with  both 
the  right  limbs,  would  insure  a succession  which  could  be  premised. 

Motions  are  as  a rule  rhythmical.  One  expects  the  serpent  to 
undulate  the  trunk  after  a regular  method,  no  matter  what  the 
speed  of  the  animal  may  be.  In  flying  and  swimming,  so  far  as 
is  known,  the  movements  are  synchronous  and  constant. 

In  the  terrestrial  movements  of  the  quadruped,  however,  such 
is  far  from  being  the  case.  This  is  owing  to  a variety  of  causes. 


60 


MATERIALS  FOR  A MEMOIR  ON 


So  far  as  the  photographs  in  the  Muybridge  series  are  concerned 
the  order  of  succession  of  foot-falls  could  have  been  improved — 
that  is  to  say,  could  have  been  more  accurate — if  the  movements 
in  the  record  of  each  gait  had  been  of  exactly  the  same  character. 
But  in  point  of  fact,  owing  to  the  practical  difficulties  surround- 
ing the  subject,  scarcely  any  two  of  the  series  begin  and  end  in  the 
same  manner,  nor  has  anything  been  recorded  of  the  mental  con- 
ditions of  the  animal,  whether  it  was  tractable  or  intractable, 
whether  excited  or  quiet,  etc., — conditions  so  essential  to  the 
manner  in  which  an  animal  may  determine  its  motions. 

If  it  can  be  conceived  that  a perfectly  tractable  and  composed 
animal  had  been  moving  in  a circle,  and  the  camerse  instead  of 
being  arranged  in  a line  had  been  grouped  in  a central  cluster  in 
such  a manner  that  they  could  secure  correct  pictures  of  the 
moving  form  in  the  same  way  as  in  the  method  actually  adopted, 
it  is  likely  that  out  of  such  an  endless  series  a uniform  set  of 
pictures  might  have  been  secured  which  would  have  given  com- 
pleteness of  representative  actions.  It  is  reasonable  to  suppose, 
that  the  motion  of  a living  creature,  as  in  an  unvital  mechanism, 
when  starting  and  when  halting,  may  be  different,  and  may  present 
contrasts  of  the  several  parts  to  a greater  degree  than  when  studied 
at  a regularly  maintained  rate,  whether  this  be  a high  or  a low 
one. 

Each  position  of  the  foot  when  three  feet  are  down  embraces 
the  laterals  with  one  of  the  opposed  feet  in  addition.  Thus,  in 
series  738,  Fig.  1,  in  addition  to  the  right  laterals  the  left  hind 
leg  is  on  the  ground.  But  in  none  of  the  pictures  were  the  left 
laterals  detected  in  which  the  right  hind  limb  was  “on.”  It  is 
probable  that  the  diagonal  heterochiral  grouping  is  a weaker  form 
of  support  than  the  lateral,  and  is  used  as  an  expedient  to  shift 
the  laterals  from  the  right  to  left  and  back. 

In  the  use  of  the  laterals,  in  all  gaits  the  feet  as  they  approach 
the  end  of  the  time  at  which  they  are  “ on”  are  at  the  side  of  the 
trunk,  while  the  feet  in  use  as  diagonals  always  remain  beneath 
the  trunk. 

The  facts  that  no  variety  of  the  deer  ever  paces,  that  the  mule- 
deer  is  the  only  variety  that  bounds, — i.e.,  that  all  the  feet  leave 
and  strike  the  ground  together, — that  the  Canadian  deer  soon 
becomes  fatigued  in  the  run,  while  this  gait  is  the  one  longest 


ANIMAL  LOCOMOTION. 


61 


assumed  by  the  Virginia  deer,*  point  to  the  conclusion  that 
natural  gaits  are  correlative  with  structural  peculiarities;  and 
while  quadrupedal  movements  are  based  on  the  same  plan,  they 
are  subject  to  modifications  in  animals  otherwise  closely  related. 

Gait  may  be  modified,  if  not  controlled,  by  the  proportion  of 
the  length  of  the  limbs  to  the  trunk.  The  hippopotamus  walks 
in  perfect  synchrony,  so  far  as  the  unaided  eye  can  detect.  The 
fat  pig  can  walk,  but  cannot  gallop.  The  lean  pig,  on  the  other 
hand,  can  gallop. 

The  fact  that  the  giraffe  is  the  only  animal  which  is  a pacer  for 
both  slow  and  fast  movements  cannot  be  easily  disassociated  from 
the  great  length  of  the  limbs. 

The  subject  of  the  gait  can  be  studied  by  observation  of  the 
animal  as  a whole,  by  numerical  analysis  of  each  foot  as  it  is 
either  “ on”  or  “ off”  the  ground,  by  numerical  analysis  of  each 
combination  of  any  number  of  feet,  and  by  graphic  analysis , by 
which  means  tracings  of  the  feet  in  combination  are  secured. 

For  convenience  the  subject  is  divided  into  the  following  heads  : 

The  Synchiral  Gaits. 

The  Heterochiral  Gaits. 

Synchikal  Gaits. 

The  Synchiral  gaits  embrace  the  canter,  the  galloj;),  and  the  run. 

In  the  canter  the  momentum  of  the  body  is  not  sufficient  to 
enable  both  the  fore  limbs  to  act  as  props  until  the  hind  limbs 
again  are  in  the  position  to  urge  the  body  forward.  Hence  the 
animal  is  observed  to  come  down  upon  a fore  limb  after  being  in 
the  air. 

In  the  gallop  the  fore  limbs  act  successively  as  props  before  the 
hind  limbs  come  down.  The  run  is  the  variety  in  which  the 
limbs  attain  the  greatest  possible  amount  of  strain,  and  in  which 
the  quick  succession  of  the  paired  feet  is  absolute. 

The  “jump”  is  an  incident  in  the  run.  In  jumping  a hurdle 
the  horse,  in  series  641,  appears  to  come  down  on  two  fore  feet  at 
the  same  moment.  In  series  637  the  horse  comes  to  the  ground 
on  the  left  fore  foot,  and  is  instantly  followed  by  the  hind  foot  of 
the  same  side. 


* J.  D.  Caton,  The  Antelope  and  Deer  of  America,  p.  270. 


62 


MATERIALS  FOR  A MEMOIR  ON 


The  Gallop . (See  pp.  41,  53.) 

In  series  632,  the  front  legs  are  “ on”  and  “ off”  equally,  each 
being  “on”  2 and  “off”  10  in  a series  of  12.  While  the  hind 
legs  are  unequal,  the  left  leg  being  “on”  5 and  “off”  7,  the  right 
is  “on”  4 and  “off”  8. 

In  series  631,  the  fore  feet  are  equal,  being  3 “on”  and  9 “off;” 
the  hind  legs  are  again  unequal,  the  left  being  “ on”  3 and  the 
right  4. 

In  series  633,  the  feet  are  all  moving  equally.  Each  foot  is 
“ on”  3 and  “ off”  9. 

It  will  be  seen  that  the  fore  feet  move  evenly  for  the  front,  and 
in  two  of  the  three  series  twice  unevenly  and  once  evenly. 

When  the  horse  is  going  at  a moderate  rate  of  speed  the  greatest 
distance  between  any  two  of  the  impressions  made  on  yielding  soil 
answers  to  the  interval  between  the  anterior  of  the  impressions  of 
the  hind  feet  and  the  first  of  the  fore  feet.  When  the  animal  is 
going  at  a high  rate  of  speed  the  greatest  distance  is  between  the 
fore  foot  by  which  he  leaves  the  ground  on  the  leap  and  the  hind 
foot  by  which  he  alights. 

In  the  canter  the  impressions  made  by  the  hind  feet  on  the  soil 
are  in  the  same  relative  positions  as  in  the  gallop, — i.e.y  they  follow 
one  another  at  wide  intervals.  The  fore  feet,  however,  yield  im- 
pressions which  lie  close  alongside  one  another, — at  about  the 
same  place. 

In  contrasting  the  two  gaits,  it  is  evident  that  in  the  canter  the 
hind  feet  act  with  such  ineffective  energy  that  the  fore  feet  are 
compelled  to  follow  each  other  in  rapid  succession  to  prevent  the 
fore  part  of  the  trunk  from  falling.  In  the  gallop  the  momentum 
of  the  body  carries  it  easily  over  both  fore  legs,  which  can  leisurely 
in  succession  act  the  part  of  vaulting-poles. 

The  gallop  as  well  as  other  gaits  show  irregularity. 

In  series  680,  oryx,  this  is  reduced  to  a minimum.  In  this  in- 
teresting series  all  the  limbs  excepting  the  right  fore  limb  are  “on” 
and  “off”  equally.  Even  in  the  right  fore  limb  the  departure 
from  uniformity  is  not  great,  the  order  being  “ on”  4 and  “off”  6. 

In  the  fallow  deer  (series  682)  the  limb-movements  are  uniformly 
“ on”  5 and  “ off”  11,  except  the  left  hind  foot,  which  stands  “ on” 
6 and  “ off”  19. 


ANIMAL  LOCOMOTION. 


63 


In  the  Virginian  deer  (series  683)  the  right  fore  limb  is  “on” 
and  “off”  13.  The  left  fore  limb  is  “on”  9 and  “off”  15.  The 
right  hind  limb  is  “on”  8 and  “off”  16,  while  the  left  hind  limb 
is  “on”  10  and  “off”  14. 

Intervals  between  the  Fore  and  Hind  Synchiries . 

The  interval  is  larger  in  the  horse  than  in  the  ungulates. ' It  is 
exceedingly  small  in  the  guanaco,  series  743. 

The  horse  may  assume  the  lateral  position  in  the  gallop,  as  is 
seen  in  series  632,  Fig.  11.  In  this  figure,  as  well  as  one  in  series 
612,  the  animal  uses  the  lateral  position  immediately  after  reaching 
the  ground . That  the  assumption  does  not  depend  on  speed  is  shown 
in  the  canter.  In  series  616  there  is  lateral  support  in  twenty-four 
pictures,  in  series  617  two  in  twelve  pictures,  and  in  series  619  one 
in  twelve  pictures. 

Heterochiral  Gaits. 

The  heterochiral  gaits  embrace  the  walk,  the  trot,  the  rack,  and 
the  pace. 

The  Walk. 

This  gait  has  been  especially  studied  from  the  figures  of  the 
series  of  the  horse,  the  buffalo,  the  ox,  the  cat,  and  the  raccoon. 

In  the  study  of  the  walk  by  the  numerical  method  it  is  found 
that  in  the  horse  (series  579),  while  the  hind  feet  are  synchronous, 
the  front  feet  are  asynchronous. 

In  the  horse  (series  574)  the  hind  limbs  are  practically  as  asyn- 
chronous as  the  fore,  while  synchrony  exists  in  the  diagonal  be- 
tween the  left  hind  limb  and  the  right  fore  limbs. 

In  the  same  series  of  twenty-four  pictures  the  following  is  the 
order  of  the  feet  that  are  “on”  and  “off :” 

Rh  “off”  14,  “on”  10. 

Rf * “ off”  9,  “on”  15. 

Lh  “on”  13,  “off”  11. 

Lf  “on”  14,  “off”  10. 

It  will  be  seen  that  the  right  hind  and  the  left  fore  legs  are 
synchronous. 

Series  579.  Rh  “on”  8,  “ off”*  4. 

Rf  “on”  7,  “off”  5. 

Lh  “ on”  8,  “ off”  4. 

Lf  « on”  9,  “ off”  2. 


64 


MATERIALS  FOR  A MEMOIR  ON 


In  the  walk  of  the  buffalo  (series  699)  the  order  is  as  follows : 
Rh  “on”  18,  “off”  6;  Rf  “on”  16,  “off”  8;  Lh  “on”  10,  “off” 
14;  Lf  “on”  15,  “off”  9. 

Nothing  here  is  synchronous ; the  greatest  discrepancy  is  seen 
in  the  diagonal  and  the  least  in  the  lateral  feet. 

In  the  ox  (series  670)  the  difference  between  the  two  fore  legs 
alone  is  great:  Rf  “on”  11,  “off”  1 ; Lf  “on”  8,  “off”  4. 

In  the  cat  (series  720):  Rf  “off”  20,  “on”  4;  Lf  “off”  15, 
“on”  9;  “Rh  “on”  9,  “off”  15;  Lh  “on”  9,  “off”  15. 

Here  all  feet  are  acting  synchronously  excepting  Rf.  Between 
the  fore  limbs  there  is  the  most  marked  difference.  The  left  fore 
limb  remains  on  the  ground  over  twice  as  long  as  its  fellow. 

In  the  horse  (series  576)  the  diagonal  Rf  and  Lh  are  “on”  8, 
“off”  4;  while  the  opposed  diagonal  is  Rh  “on”  11,  “off”  11 ; 
and  Lf  “ on”  6,  and  “ off”  6. 

The  walk  in  the  raccoon  (series  744)  shows  that  the  fore  leg 
moves  slower  than  the  hind  leg.  When  the  momentum  of  the 
animal  is  increased  the  fore  leg  attains  the  same  speed  of  rapid 
change  as  the  hind. 

The  rate  of  the  “on”  and  “off”  of  the  fore  feet  is  J to  J,  while 
in  the  horse  (series  579)  the  rate  is  § “ on”  to  J “ off.” 

The  left  fore  foot  is  “on”  the  ground  in  1,  2,  3,  10,  11,  12,  13. 
14,  20,  21,  22,  23,  = 12. 

The  left  fore  foot  is  “off”  the  ground  in  4,  5,  6,  7,  8,  9,  15, 
16,  17,  18,  19,  24,  = 12. 

The  left  hind  limb  is  “on”  in  1,  8,  9,  10,  11,  17,  18,  19,  — 8. 

It  is  “off”  in  2,  3,  4,  5,  6,  7,  12,  13,  14,  15,  16,  20,  21,  22, 
23,  24,  = 16. 

Thus  the  left  fore  foot  is  in  the  act  of  supporting  and  propel- 
ling the  body  for  the  same  length  of  time  as  it  is  engaged  in  pre- 
paring for  a second  stoke.  In  the  left  hind  foot  the  time  of  the 
foot  when  engaged  in  support  or  propulsion  is  but  one-half  that 
of  the  time  when  it  is  engaged  in  the  air. 

Combinations  in  the  Walk. 

Out  of  the  number  of  combinations  which  it  is  possible  to 
secure  from  the  feet  when  on  the  ground  the  following  is  the 
arrangement  most  frequently  seen  in  the  act  of  walking : Two 
hind  feet  alone ; two  fore  feet  alone ; two  hind  feet  and  two  fore 


ANIMAL  LOCOMOTION. 


65 


feet.  The  combination  one  hind  foot  and  two  fore  feet  has  not 
been  seen,  though  no  reason  can  be  urged  for  the  non-occurrence. 
(See  especially  series  744.) 

Support  of  the  Vertebral  Column  in  the  Walk. 

The  lateral  disposition  of  the  feet  in  the  walk  supports  the 
vertebral  column  at  the  ends,  and  the  figure  of  the  trunk  and 
limbs  compares  with  a truncated  triangle  whose  base  is  on  the 
ground.  In  the  diagonal  disposition  the  opposed  feet  meet  at  a 
point  near  each  other  under  the  centre  of  the  trunk  (when  the 
other  feet  are  u off”),  and  the  figure  compares  with  that  of  an  in- 
verted triangle  whose  curved  base  is  directed  upward. 

The  animals  which  assume  the  diagonal  central  support  are 
short-legged  creatures.  The  best  examples  are  the  raccoon  and 
the  baboon.  (See  p.  72  and  p.  75.)  The  approximation  to  it  is 
seen  in  the  capybara.  It  is  never  seen  in  the  ungulate. 

The  Trot. 

In  the  trot  the  succession  of  foot- falls  is  inclined  to  synchrony 
from  the  circumstance  that  the  motion  becomes  more  constant  as 
the  animal  increases  in  speed. 

Thus,  in  the  trot  in  a series  of  twenty  pictures, 

Rh  is  “off”  15, 

“ on”  5. 

Lf  is  “off”  15. 

“ on”  5. 

In  593 — another  series — the  order  is  as  follows  in  a series  of 
twelve  pictures : 


Rh 

is 

(( 

on” 

5. 

a 

off” 

7. 

Lh 

is 

u 

on” 

9. 

u 

off” 

3. 

Rf 

is 

« 

on” 

4. 

u 

off” 

8. 

Lf 

is 

i( 

off” 

9. 

u 

on” 

3. 

The  left  feet  have  moved  in  synchrony.  The  right  feet  show 
a disposition  to  remain  on  ground  longer,  and,  therefore,  are  doing 
more  work. 


66 


MATERIALS  FOR  A MEMOIR  ON 


In  the  trotting-horse  the  fore  leg  which  is  about  to  leave  the 
ground  is  apt  to  interfere  with  the  hind  leg  of  the  opposite  side 
as  it  is  advancing  to  come  to  the  ground.  In  order  to  avoid  this 
mishap  the  animal  is  trained  to  lift  the  fore  legs  to  a degree  which 
is  not  required  in  the  walk.  The  motions  of  the  animal  suggest 
that  the  act  of  trotting  as  developed  in  the  horse  for  fast  gaits  is 
artificial  and  is  not  especially  useful  for  studies  in  locomotion.  It 
has  the  same  value  as  the  study  of  the  motions  of  a “ trick-horse. ” 
(See  p.  56.) 

The  Rack. 

That  the  rack  is  not  a uniform  gait  is  seen  from  the  following 
statements : 

In  594,  in  a series  of  twelve  pictures,  the  animal  stands  on  one 
foot  alone  once ; is  in  the  air  in  six ; and  on  laterals  in  five. 

In  595,  in  a series  of  the  same  length,  one  foot  remains  “on”  in 
three;  laterals  are  “on”  in  six;  and  the  animal  is  “off”  in  three. 

The  transition  between  laterals  is  well  seen  in  the  series  593. 
In  the  walk  at  least  the  transition  between  the  laterals  and  the 
diagonals  is  effected  by  the  hind  limbs. 

In  racking  the  impressions  made  by  the  hoofs  on  the  ground 
are  in  regular  alternation  of  front  and  hind  feet. 

Pacing  in  the  horse  is  a delicate  motion,  since  any  irregularity 
of  the  ground  interferes.  The  giraffe  is  a natural  pacer.  The 
pace  is  often  accepted  by  the  dog. 

Transitions  and  Contrasts  of  Gait. 

The  walk  is  the  basis  of  the  trot  and  the  amble,  which  is  in- 
deed nothing  but  a running  walk.  The  gallop  leads  to  the  run. 
The  run  may  be  called  an  extended  gallop.  The  amble  and  the 
rack  are  trained  forms  of  the  gait.  The  walk  often  breaks 
directly  into  the  amble,  and  this  into  the  gallop. 

The  difference  between  the  trot  and  the  pace,  as  noticed  in  the 
effect  the  positions  of  the  limbs  make  on  the  eye,  is  but  slight. 

In  series  602,  Fig.  4,  the  fore  and  hind  legs  on  the  right  side 
are  both  in  forward  strain.  The  fore  leg  comes  down  first,  and  is 
instantly  followed  by  the  hind.  If  the  two  had  come  down  to- 
gether, we  should  have  had  the  initial  step  of  the  pace. 

The  trot  and  the  walk  are  closely  allied  in  all  essential  particu- 
lars. The  manner  in  which  the  imprints  of  the  feet  are  made  on 


ANIMAL  LOCOMOTION. 


67 


the  ground  is  in  both  gaits  the  same.  The  front  and  hind  feet  of 
heterochiral  pairs  impress  the  ground  at  the  same  places.  The 
intervals  between  the  sets  of  heterochiral  impressions  are  in  the 
walk  about  thirty-eight  inches ; in  a small  horse  they  may  be 
twenty-five  inches.  The  contrasts  between  the  figures  in  the 
photographs  of  the  horse  at  the  walk  and  at  the  trot  are  very 
pronounced  in  the  profiles.  (See  series  584  and  601.)  But  in  the 
foreshortenings  the  two  gaits  present  appearances  which  are  very 
similar.  The  reader  may  compare  Figs.  4 to  8 with  profit. 

The  trot  and  the  walk  are  both  heterochiral,  and  vary  in  the 
manner  of  lateral  or  diagonal  positions  of  limbs. 

The  chief  difference  between  the  impressions  made  on  yielding 
ground  of  the  feet  in  the  trot  and  the  walk  is  seen  in  the  relative 
distance  between  them.  The  impressions  are  much  farther  apart 
in  the  trot  than  in  the  walk. 

Gaits  are  more  variable  in  the  slow  than  in  the  fast  varieties. 
This  is  inevitable,  since  the  fast  gaits  depend  upon  uniformity.  Dr. 
Cryer,  in  conversation  with  the  writer,  states  this  as  an  impression. 

The  Laterals  in  the  Walk  and  the  Rack  contrasted. 

The  lateral  position  as  seen  in  the  walk  is  essentially  different 
from  that  seen  in  the  rack.  In  the  walk  the  fore  foot  is  in  for- 
ward strain,  while  the  hind  limb  is  in  backward  strain.  In  the 
rack,  the  fore  foot  being  in  forward  strain,  the  hind  foot  is  in  the 
same  position,  so  that  the  limbs  are  parallel  to  each  other. 

In  Procyon  (series  744),  the  diagonal  heterochiry  shows  that  the 
fore  and  the  hind  leg,  say  of  the  right  side,  are  both  in  forward 
movement,  while  the  fore  and  the  hind  leg  of  the  left  side  are  in 
backward  movement. 

In  lateral  heterochiry  the  disposition  is  reversed  : when  the 
fore  limb  is  in  forward  movement  the  hind  limb  of  the  same  side 
is  in  backward  movement. 

The  graphic  method  of  analysis  embraces  the  following  consid- 
eration: The  essential  lines  in  a given  movement  have  been  drawn 
and  arranged  in  the  same  order  as  in  the  photographs.  (See  series 
577.)  As  the  walk  is  the  most  complicated  of  the  gaits,  it  has 
been  selected  as  an  example  of  this  method.  The  advantage  is 
evident,  for  the  observer  is  relieved  of  the  action  of  but  one  pair 


68 


MATERIALS  FOR  A MEMOIR  ON 


of  feet.  The  eye  can  pass  easily  from  the  combination  of  left 
hind  and  right  fore  feet — as  in  the  line  to  the  left — to  that  of  the 
right  hind  and  left  fore  feet  of  the  lower  lines  to  the  right ; and 
the  plate  itself  being  before  the  observer,  the  study  of  the  suc- 
cession of  foot-falls  becomes  an  easy  matter. 


The  Graphic  Method  of  Analysis. 


The  Limbs  of  the  Horse  at  a Walk  in  Diagonal  Heterochiry. 
(Series  577.  See  pp.  64,  67.) 


Eh  “off.”  Lf“on.” 


Lh“on.”  Ef“off.’ 


Eh  “ on.”  Lf  “ on.”  Lh  “ off.”  Ef  “ off.’ 


ANIMAL  LOCOMOTION, 


69 


4. 


o. 


6. 


70 


MATERIALS  FOR  A MEMOIR  ON 


8. 


9 


ANIMAL  LOCOMOTION. 


71 


Rli  “ on.” 


Lf  “ on.” 


Lh  “ off. 


Ef  “off.1 


72 


MATERIALS  FOR  A MEMOIR  ON 


An  Analysis  of  the  Movements  of  the  Raccoon,  the 
Baboon,  and  the  Sloth. 

In  addition  to  the  general  remarks  on  animal  movement  and 
the  analysis  of  separate  phases  of  the  limb  positions,  it  has  been 
thought  advisable  to  describe  a few  forms  in  detail. 

With  this  object  in  view,  figures  of  the  raccoon  (series  744), 
the  baboon  (series  747),  and  the  sloth  (series  750)  are  herewith 
presented. 

The  Raccoon . (Series  744.) 

The  raccoon  (Procyon)  has  been  accepted  as  a form  worthy  of 
careful  analysis,  since  the  genus  is  one  of  the  most  ancient  of  the 
extant  Carnivora,  and  presents  in  its  gait  opportunity  for  ascertain- 
ing the  manner  in  which  a primitive  flesh-eater  moved  when  of 
small  size  and  of  short  limb.  (See  p.  38.) 

The  gait  from  Fig.  1 to  Fig.  4 is  in  diagonal  heterochiry.  In 
Fig.  1 the  right  fore  foot  lingers  so  long  on  the  ground  that  the 
left  hind  foot  is  about  to  come  “ on”  also.  The  right  hind  foot  is 
about  leaving,  and  the  fifth  toe  projects  backward.  (See  p.  51.) 


(Fig.  2 of  series.) 


In  Fig.  2 the  right  fore  foot  remains  on  the  ground,  the  left  hind 
foot  now  reaches  the  ground  at  its  side,  and  the  right  hind  foot  is 
“ off.”  The  position  is  retained  in  Figs.  3,  4,  and  5. 

In  Figs.  5,  6,  7 the  gait  is  left  lateral  heterochiry,  the  support 
being  on  the  left  legs,  the  fore  limb  being  in  forward  movement 
and  the  hind  limb  being  in  backward  movement.  Fig.  8 is  a 
transitional  form  (the  animal  movement  only  resting  on  three 
legs)  back  to  the  diagonal  heterochiry,  as  seen  in  Fig.  9,  which 
retains  the  combination  in  one  picture  only,  to  be  again  in  right 


ANIMAL  LOCOMOTION. 


73 


lateral  heterochiry  in  Figs.  10,  11,  12.  The  fifth  toe  of  the  right 
hind  foot  is  here  seen  to  extend  horizontally.  The  change  to 


(Fig.  3 or  series.) 


diagonal  heterochiry  is  made  in  Figs.  13, 14  (which  are  repetitions 
of  Figs.  1,  2,  3),  and  a stride  is  completed.  The  animal  now 
alters  its  gait  from  heterochiry  to  synchiry.  Fig.  15  is  the  form 
of  transition.  In  Fig.  16  the  change  has  been  completed  and  the 
animal  is  sustained  alone  by  both  hind  feet.  He  maintains  this 
position  in  Fig.  17,  but  again  is  in  a transition  form  of  three  legs 
on  the  ground  in  Fig.  18. 


74 


MATERIALS  FOR  A MEMOIR  ON 


In  Fig.  19  the  animal  is  in  diagonal  heterochiry,  in  which 
position  the  right  hind  leg  shows  the  fifth  toe  in  the  axis  of  the 
leg,  and  greatly  abducted  from  the  fourth. 


(Fig.  19  or  series.) 


In  Fig.  20  it  is  again  synchiral,  the  fore  pair  now  assuming 
the  work  of  supporting  the  body.  The  fore  limbs  are  nearly  at 
the  extremes  of  forward  and  backward  movement. 

The  sole  of  the  foot  in  the  left  fore  foot  is  in  part  in  aid  of 
the  limb,  and  presents  an  example  of  the  plantigrade  foot  be- 
coming semi-digitigrade  as  the  foot  passes  backward  of  the  vertical 
line. 


(Fig.  20  of  series.) 


It  will  be  seen  that  the  gait  is  irregular ; it  is  first  a walk  or 
trot,  afterwards  assumes  the  position  of  pacing,  and  finally  ends  in 
a gallop,  or  as  much  of  the  latter  gait  as  can  be  assumed  to  exist 
in  an  animal  with  short  legs; 

The  Baboon.  (Series  747.) 

In  the  series  of  the  baboon  the  animal  is  seen  in  the  walk. 
The  form  was  accepted  for  comparison  with  the  raccoon  because 
of  the  position  of  the  animal  near  the  other  end  of  the  scale  of 
quadrupeds.  The  limbs  have  great  length,  and  the  intervals  be- 


ANIMAL  LOCOMOTION. 


75 


tween  the  two  feet  of  a single  pair  when  in  extremes  of  forward 
and  backward  movement  are  correspondingly  great. 

In  Fig.  1 the  animal  has  just  left  lateral  support,  in  which 
both  limbs  move  in  the  centre  of  the  body  by  the  left  fore  foot 
leaving  the  ground.  In  Fig.  2 the  support  is  diagonal,  and  both 
limbs  (right  fore  and  left  hind)  are  removed  from  the  centre. 
This  is  retained  through  Figs.  3 and  4.  In  Fig.  5 the  same  dis~ 


(Fig.  5 of  series.) 


position  continues,  but  it  is  noteworthy  because  of  the  shape  of 
the  left  hind  limb,  which  resembles  the  shape  of  the  ungulate 
foot.  The  right  fore  limb  is  now  in  the  extreme  of  backward 
movement. 


(Fig.  6 of  series.) 


In  Figs.  6 and  7 the  position  is  left  fore  and  right  hind  (lateral 
heterochiry). 


76 


MATERIALS  FOR  A MEMOIR  ON 


In  Fig.  8 the  laterals  have  changed  to  diagonals  by  the  right 
fore  foot  coming  down  as  the  left  leaves  the  ground. 


(Fig.  7 or  series.) 


In  Figs.  9,  10,  and  11  the  same  position  is  maintained.  The 
shape  of  the  right  fore  leg  as  it  nears  the  vertical  position  is  note- 
worthy. 


(Fig.  8 of  series.) 


The  left  hind  foot  has  overtaken  the  lingering  right  fore  foot, 
and  three  feet  are  on  the  ground.  This  position  is  instantly  lost 
by  the  lifting  of  the  left  hind  foot  from  the  ground,  when  a diag- 
onal support  ensues,  which  closely  resembles  in  general  effect  the 
lateral  support  in  Fig.  6. 


ANIMAL  LOCOMOTION. 


77 


(Fig.  11  of  series.) 


(Fig.  12  of  series.) 


(Fig.  13  of  series.) 


78 


MATERIALS  FOR  A MEMOIR  ON 


This  position  is  maintained  in  Fig.  14.  Fig.  14  is  a repetition 
of  Fig.  1,  and  the  stride  is  complete.  The  gait  is  shifted  to  left 
laterals  in  Figs.  15  and  16. 


(Fig.  14  of  series.) 


Figs.  13  and  14  can  be  compared  with  advantage  with  Figs.  3 
and  4, 13  and  14  of  Procyon  (series  744).  The  feet  are  relatively 
in  the  same  position. 

In  the  baboon  the  dorsal  line  changes  scarcely  at  all  from  that 
in  the  other  figures.  In  Procyon  the  dorsal  line  is  more  convex 
in  these  figures  than  in  any  others. 

The  most  characteristic  position  of  Procyon  is  the  laterals  in 
Figs.  11  and  12.  The  limbs  are  in  the  extreme  of  movement, 
the  hind  backward  and  the  fore  forward.  The  most  character- 
istic position  of  the  baboon  (Fig.  6)  is  the  reverse  of  this,  the  hind 
limb  being  forward  and  the  fore  backward.  The  relative  places 
of  the  “on”  and  “off”  feet  are  directly  opposed. 

The  Sloth.  (Series  750.) 

The  sloth  does  not  use  the  limbs  in  lateral  heterochiry.  He  is 
compelled  to  keep  the  feet  “on”  in  combinations  which  will  insure 
his  support.  Owing  to  the  hook-like  grasp  of  the  feet,  the  hind 
limb  becomes  markedly  rotated  outward  as  it  passes  back  of  the 
vertical  line  (see  p.  38). 

Fig.  1 is  in  the  same  position  as  in  the  baboon  (Figs.  6 and  7), 
— i.e .,  the  fore  and  hind  limb  of  the  same  size  (viz.,  the  left) 
are  at  the  nearest  point  possible  one  to  the  other.  But  the  other 
two  limbs,  while  lying  at  the  farthest  point  possible  from  each 


ANIMAL  LOCOMOTION. 


79 


(Fig.  1 of  series.) 


80 


MATERIALS  FOR  A MEMOIR  ON 


other,  are  not  “off,”  as  is  the  case  with  the  baboon.  Save  in  this 
instance,  the  positions  are  the  same. 

The  attitude  remains  unchanged  in  Fig.  2.  In  Fig.  3 the  left 
fore  limb  has  left  the  perch,  and  is  projected  directly  upward. 


(Fig.  4 of  series.) 


In  Figs.  4 and  5 the  left  fore  limb  is  swung  forward  above  the 
level  of  the  perch,  and  the  right  hind  leg  is  “ off”  and  projects 


(Fig.  5 of  series.) 


upward.  In  Fig.  6 all  limbs  are  again  “ on,”  as  in  Fig.  1.  The 
left  fore  and  the  right  hind  limb  have  just  come  “on.”  The 
position  is  maintained  through  Figs.  7,  8,  and  9. 


ANIMAL  LOCOMOTION. 


81 


(Pig.  6 or  series.) 


6 


82 


MATERIALS  FOR  A MEMOIR  ON 


Figs.  7 and  8 closely  resemble  each  other.  They  differ  in  the 
degree  of  outward  rotation  of  the  left  hind  leg.  It  is  wider  in 
Fig.  8 than  Fig.  7,  and  is  rotated  farther  outward.  The  head  in 
Fig.  8 is  nearer  the  beam  than  in  Fig.  7.  For  consideration  of 
the  outward  rotation,  see  p.  89. 

In  the  interval  between  Figs.  9 and  10  both  the  left  hind  and 


(Fig.  9 of  series.) 


the  right  fore  limb  have  left  the  perch  and  remain  “off”  through 
the  remaining  Figs.  11  and  12. 

In  Figs.  10,  11,  and  12  the  manner  in  which  the  support  is 
maintained  while  the  two  limbs  are  “off”  is  illustrated.  It 'is 


ANIMAL  LOCOMOTION. 


83 


strictly  diagonal  heterochiry.  Yet  in  Fig.  12  the  same  positions 
as  in  Figs.  1,  6,  7,  8,  and  9 are  about  to  be  assumed,  showing  that, 


(Fig.  11  of  series.) 


while  support  may  be  diagonal,  the  limbs  which  relatively  are 
farthest  apart  or  the  nearest  together  are  laterals.  Thus  the  gait 

(Fig.  12  of  series.) 


of  the  sloth  is  peculiar  in  having  all  four  feet  “on”  at  one  stage 
of  movement,  while  the  gait  is  the  usual  disposition  of  alternate 
feet  by  diagonal. 


84 


MATERIALS  FOR  A MEMOIR  ON 


ZOOLOGICAL  CONSIDERATIONS. 

The  object  which  the  writer  has  had  constantly  in  view  in 
studying  the  photographs  is  to  endeavor  to  determine  the  value 
of  attitude  and  gait  to  classification.  Many  of  the  notes  bear  to 
a greater  or  less  extent  upon  zoology,  but  a few  which  appear  to 
apply  in  an  especial  way  to  taxonomy  are  conveniently  brought 
together  at  this  place. 

As  is  well  known,  the  manus  and  pes  present  a plan  in  the 
arrangement  of  the  elements  which  may  conveniently  receive  the 
name  of  the  lateral  and  median  series.  In  the  manus,  the  cunei- 
form and  the  unciform  bones  constitute  the  lateral,  and  all  the  re- 
maining bones  the  median,  series.  In  the  pes,  the  calcaneum  and 
cuboid  bone  are  embraced  in  the  lateral  series,  and  all  the  remain- 
ing bones  form  the  median.  With  this  necessary  understanding, 
the  writer  will  now  proceed  to  state  the  premise  upon  which  he 
undertook  a special  examination  of  the  manus  and  pes  in  connec- 
tion with  the  phenomena  of  limb-movement.  The  episode  may 
be  accepted  as  an  instance  in  which  the  photographs  suggest  vari- 
ous lines  of  research,  even  though  nothing  of  especial  value  be 
claimed  for  the  results  here  secured. 

When  it  was  determined,  chiefly  by  the  study  of  the  stroke  (see 
p.  50),  that  the  foot  comes  down  by  the  outer  border  and  leaves 
by  the  inner,  an  attempt  was  made  to  ascertain  by  examination  of 
the  structure  of  the  carpus  and  tarsus  the  mechanism  which  corre- 
lated with  the  movement.  It  was  expected  that  an  oblique  line 
by  which  the  strain  could  be  traced  across  the  small  bones  would 
be  found.  The  views  of  Leboucq,*  which  embrace  a path  of 
precisely  this  character  in  the  embryonic  form  of  the  tarsus  of 
mammals,  appeared  to  be  confirmatory  of  this  expectation. 

The  well-known  fact  that  the  calcaneum  occasionally  ossifies 
with  the  scaphoid  bone  in  the  human  foot,f  and  is  at  times  found 
united  to  it  by  synchondrosis, J was  suggestive  that  the  oblique 
axis  could  be  determined  in  that  form  with  whose  structure  anat- 


* Arch.  Biol.  (Brussels),  iv.  35. 

f Gruber,  Mem.  de  l’Acad.  de  St.  Petersbourg,  ser.  vii. , p.  9,  Taf.  xvii. ; 
Holl,  Arch,  fiir  Klin.  Chirurg.,  1880;  Zuckerkandl,  Wiener  Med.  Jahrbuch, 
1880. 

X Weber  M.,  Verslag.  der  kon.  Ak.  Amsterdam,  1883,  xviii.  121. 


ANIMAL  LOCOMOTION. 


85 


omists  are  most  familiar.  Aeby*  describes  a similar  arrange- 
ment in  the  foot  of  the  gorilla. 

It  was  reasonable  to  infer  from  these  data  that  the  disposition 
of  the  calcaneum  to  transfer  the  strain  transmitted  to  it  across  the 
foot  to  the  scaphoid  would  characterize  the  mammalian  foot. 

A careful  examination  of  the  tarsus  has  not  warranted  the  in- 
ference. As  shown  bv  Leboucq,  the  arrangement  exists  in  the 
embryo,  but  it  is  not  maintained  as  a rule  in  the  adult,  nor  is  it 
seen  in  the  phylogeny  of  the  group. 


Fig.  2.  Fig.  3.  Fig.  4. 


Fig.  2. — Diagram  of  the  relation  of  the  astragalus  (A),  the  calcaneum  (Cn),  the  scaphoid 
bone  (S),  and  the  cuboid  bone  (Cb)  in  the  foot  of  mammals. 

Fig.  3. — Diagram  to  exhibit  the  disposition  for  the  astragalus  to  form  a junction  with 
the  cuboid  bone.  (Letters  as  in  Fig.  2.) 

Fig.  4. — Diagram  to  exhibit  a disposition  for  the  calcaneum  to  form  a junction  with 
the  scaphoid  bone.  (Letters  as  in  Fig.  2.) 

The  statement  of  Ivowalevnsky  is  accepted,  that  the  earlier 
forms  of  mammals  exhibit  lines  of  support  which  correspond  to 
the  arrangement  of  the  bones  of  the  leg.  (See  Fig.  2.)  But  in  the 
animals  now  living,  the  lines  of  the  bones  of  the  carpus  and  tarsus 
do  not  as  a rule  show  such  independence.  The  bones  of  the  tar- 
sus are  almost  invariably  more  or  less  displaced.  In  the  tapir 
and  the  rhinoceros,  which  are  the  best  living  examples  of  related 
forms  to  the  earlier  forms,  the  acquired  support  from  adjusting 
rows  is  as  exact  as  in  any  of  the  numerous  recent  specialized 
forms  which  at  present  inhabit  the  earth. 

So  far  as  examined,  the  calcaneum  articulates  with  the  scaphoid 
bone  in  the  following  genera  only : 

Homo,  Dipus, 

Troglodytes,  Ccelogenys, 

Equus (variable;  sometimes  Erethizon  (variable), 

astragalo-cuboid), 


* Morph.  Jahrbuch,  iv.,  1878. 


86 


MATERIALS  FOR  A MEMOIR  ON 


Herewith  are  given  examples 
loid  articulation  : 

Hyrax  (not  marked), 
Rhinoceros, 

Amynodon, 

Ungulata, 

Procyon, 

Ursus, 

Erignathus, 

Menodus, 

Palseosyops, 

Creodonta, 

Neither  the  calcaneo-scaphoid 
tion  is  found  in  the  following : 


the  common  cuboido-astraga- 

Macropus, 

Phascalarctos, 

Dicotyles, 

Hippopotamus, 

Erethizon  (variable), 
Arctomys, 

Myrmecophaga, 

Elephas, 

Equus  (variable;  sometimes 
calcaneo-scaphoid). 
nor  cuboido-astragaloid  articula- 


Orycteropus (variable;  tends 
to  calcaneo-scaphoid), 
Homo  (variable;  sometimes 
calcaneo-scaphoid). 


Dasyprocta, 

Capromys, 

Fiber, 

Hystrix, 

Hyena  crocuta, 

While  a fixed  arrangement  of  the  parts  in  an  assumed  oblique 
axis  is  thus  undetected,  the  examination  was  fruitful  of  one  result, 
- — namely,  that  when  in  addition  to  the  axial  disposition  of  the 
tarsal  bones  one  to  another  and  the  lateral  adaptation  of  parts  in 
transverse  rows  was  departed  from,  the  departure  took  place  in 
one  of  two  ways, — either  by  the  calcaneum  reaching  the  scaphoid 
(i.e.j  by  a direction  downward  and  inward)  or  by  the  cuboid  bone 
reaching  the  astragalus  ( i.e .,  by  a direction  upward  and  inward). 
It  is  thus  demonstrable  that  the  elements  in  the  tarsus  which  first 
distribute  the  weight  of  the  outer  border  of  the  foot  as  it  comes 
to  the  ground  transmit  the  impact  inward  in  an  oblique  manner, 
and,  it  may  be  assumed,  tend  to  throw  the  weight  of  the  limb 
towards  its  axial  line,  which  sustains  the  weight  of  the  body 
when  the  limb  is  in  the  vertical  position. 

In  the  study  of  the  phytogeny  it  will  be  seen  that  the  more 
distal  of  the  two  bones  is  first  pressed  inward,  and  that  this 
arrangement  obtained  not  only  in  the  first  (with  the  exception  of 
Coryphodon),  but  in  most  of  the  extant  forms.  Why  it  should 
ever  have  departed  from  this  arrangement  and  reversed  the  in- 
ward impact  to  the  calcaneum  is  not  an  easy  question  to  answer. 


ANIMAL  LOCOMOTION. 


87 


It  is  worthy  of  remark  that  in  Equus  and  Dipus  we  have  highly 
specialized  forms  of  foot-structures ; and  in  Primates,  while  the 
foot  on  the  whole  is  generalized,  the  astragalus  sends  a remark- 
ably inward  directed  and  obliquely  placed  neck  in  a direction 
which  would  render  it  difficult  for  the  cuboid  bone  to  reach  it. 

It  must  be  acknowledged  as  a great  difficulty  how  an  inter- 
mediate group  arose  in  which  a simple  form  of  tarsal  disposition 
is  retained.  While  from  facts  presented  by  Professor  Flower  it 
would  be  natural  to  assume  that  Orycteropus  might  move  the 
foot  in  a manner  different  from  Myrmecophaga,  nothing  can  be 
urged  why  Hyena  should  differ  from  Canis,  or  Dasyprocta  and 
Capromys  from  Arctomys, 

An  examination  of  the  carpus  showed  less  disposition  for  the 
outer  elements  of  the  series  to  be  placed  inward  than  is  the  case 
in  the  tarsus.  The  cuneiform  bone,  which  corresponds  in  position 
to  the  calcaneum,  and  the  unciform,  which  corresponds  to  the 
cuboid  bone,  remain  in  all  forms  of  the  manus  in  constant  relation 
to  the  rest  of  the  carpus.  But  the  entire  lateral  division  of  the 
carpus  exerts  a disposition  to  displace  the  os  magnus  inward  and 
upward  in  a manner  which  is  strikingly  exhibited  in  the  follow- 
ing scheme. 

The  os  magnum  articulates  with  the  scaphoid  bone  in 
Coelogenys,  Tapirus, 

Rhinoceros,  Sus, 

Dicotyles,  Chrysochloris. 

Hippopotamus, 

That  is  to  say,  the  os  magnum,  in  addition  to  articulating  with 
its  own  axially  disposed  element,  the  lunare,  secures  an  articula- 
tion with  the  scaphoid  bone. 

The  os  magnum  articulates  with  the  lunare  only  in 

Dasyprocta,  Elephas  (variable  with 

Capromys,  trapezoidal-lunare), 

Erethizon,  Tapirus, 

Hyrax,  Manatus, 

Hystrix,  Orycteropus, 

Arctomys,  Myrmecophaga, 

Uintatherium,  Myogale. 

In  summarizing  these  results,  it  may  be  said  that  the  fact  of  the 
outer  border  of  the  pes  coming  to  the  ground  in  the  first  stage  of 


88 


MATERIALS  FOR  A MEMOIR  ON 


the  stroke  is  in  correlation  with  a disposition  for  one  or  more  of 
the  tarsal  elements  of  the  outer  series  to  secure  junctures — i.e ., 
junctures  not  accounted  for  in  the  plan  of  the  parts — with  one  or 
more  elements  of  the  median  series.  Relatively  few  genera  resist 
this  disposition. 

In  the  manus,  the  lateral  series  remains  intact,  hut  in  a few  ex- 
tant genera  and  in  some  extinct  genera  the  outermost  of  the  median 
series  is  seen  to  articulate  with  a carpal  element  which  lies  to  its 
inner  side. 

Deviations  of  the  Trunk  with  Respect  to  a Hypothetical  Longitudi- 
nal Axis. 

An  interesting  series  of  comparisons  can  be  instituted  between 
the  anterior  and  the  posterior  parts  of  the  trunk  in  the  various 
positions  of  the  limbs.  In  illustration  of  this  subject  attention  is 
directed  to  the  deviations  of  the  trunk  in  advance  of  the  rump 
with  respect  to  a line  drawn  horizontally  forward  from  the  base 
of  the  tail.  Assuming  that  the  beginning  of  such  a line  corre- 
sponds to  the  part  which  shows  the  least  motion  and  passes  to 
that  which  shows  the  most,  it  will  follow  that  the  fore  part  of  the 
trunk,  together  with  the  whole  of  the  regions  of  the  head  and  the 
neck,  will  shift  positions  with  respect  to  this  line.  In  series  675 
the  figures  of  the  hog  demonstrate  that  the  body  in  advance  of 
the  rump  are  highest  when  the  animal  is  resting  on  both  hind 
feet.  It  is  next  highest  when  the  animal  has  come  down  one 
fore  foot.  In  the  deer,  when  propped  on  the  fore  limbs,  the  animal 
sinks  so  low  anteriorly  as  to  permit  the  horizontal  line  to  intersect 
the  muzzle.  The  fact  that  the  baboon  exhibits  no  contrast  of 
the  kind  named  would  lead  to  the  conclusion  that  the  clavicle 
prevents  the  fore  part  of  the  trunk  from  sinking, — a conclusion 
which  is  invalidated  by  the  fact  that  the  elephant  shows  a similar 
exemption. 

Relation  between  the  Oblique  Movement  across  the  Foot  and  the 

Number  of  Toes. 

From  the  fact  that  the  outer  border  of  the  foot  first  strikes  the 
ground  and  that  the  inner  border  last  leaves  it,  one  can  create  a 
proposition  to  which  the  following  facts  are  corollary.  (See  pp. 
42,  50.) 


ANIMAL  LOCOMOTION. 


89 


When  the  outer  border  is  longer  and  stouter  than  the  inner, 
the  first-named  parts  of  support  are  of  more  importance  than  the 
last.  The  difference  in  this  regard  between  the  foot  of  man  and 
that  of  the  bear  should  be  the  difference  between  the  respective 
lengths  of  the  first  and  the  fifth  toes. 

When  the  inner  toe  is  rudimental,  or  lost,  the  foot  has  left  the 
ground  before  the  inner  border  is  reached.  But  it  is  not  so  evident 
why  the  fifth  toe  should  be  lost.  One  would  suppose  that  this  toe 
would  be  the  most  persistent.  The  sequence  of  the  limbs  of  the 
horse  from  the  five-  to  the  single-toed  forms  would  be  of  interest 
to  study  in  this  connection. 

Rotation  of  the  Limb. 

In  another  relation  than  that  included  in  the  foregoing  the 
study  of  the  photographs  has  been  of  interest.  Allusion  is  partic- 
ularly made  to  the  forward  swing  of  the  fore  limb  and  the  outward 
rotation  of  both  limbs  (for  inward  rotation  see  p.  59). 

The  extent  of  the  forward  swing  is  found  to  correspond  to  the 
extent  of  the  trochlear  surface  of  the  humerus  as  it  enters  into 
the  composition  of  the  elbow-joint.  In  addition  to  this  fact  atten- 
tion may  be  called  to  the  difference  in  the  length  of  the  olecranon 
in  different  animals.  The  olecranon  is  greatly  longer  relatively 
to  the  shaft  of  the  ulna  in  primitive  types  of  Mammalia  than  in 
the  more  specialized,  as  the  writer  has  been  informed  by  Professor 
W.  B.  Scott.  The  same  difference  is  found  to  obtain  between 
Dicotyles  and  Sus.  May  it  not  be  claimed  that  the  difference 
correlates  with  the  facilities  possessed  of  maintaining  the  fore  limb 
in  backward  strain?  The  enormous  leverage  secured  by  a long 
olecranon  must  enable  the  limb  to  maintain  a strong  position  for 
the  limb  when  it  is  held  in  backward  strain  as  compared  to  one 
in  which  the  olecranon  is  short.  This  must  be  especially  marked 
when  the  humerus  is  long,  as  is  always  the  case  in  these  types. 

The  mechanism  which  accompanies  the  rotation  of  the  limb 
outward  at  the  knee  after  it  has  passed  the  vertical  line  is  as- 
sociated, as  has  been  seen,  with  inward  rotation  of  the  hock. 
This  form  of  torsion  is  described  (see  p.  45),  and  the  springing 
power  of  the  limb  is  a resultant.  The  amount  of  springing  power 
should  correlate  with  the  torsion,  and  the  facets  by  which  twists 
are  effected  be  indices  of  the  act.  The  conversion  of  the  calcaneo- 


90 


MATERIALS  FOR  A MEMOIR  ON 


cuboidal  articulation  into  a convexo-concave  joint,  in  forms  in 
which  the  oblique  impact  is  cuboido-astragaloid,  would  look  as 
though  such  impact  favored  torsion. 

The  study  of  the  rotation  of  the  limb  is  conveniently  under- 
taken in  the  elephant,  since  the  fur  is  here  absent.  A number 
of  the  positions  assumed  by  the  limbs  is  illustrated  in  series 
733,  Figs.  1 to  12.  (See  the  figures  of  the  fore  limb  of  the 
elephant.) 

The  width  of  the  limb  at  the  elbow  is  observed  to  be  less  ill 
backward  strain  than  in  the  recover. 

In  Figs.  1,  2,  3,  and  4 the  olecranon  is  in  line  with  the  posterior 
border  of  the  arm  above  the  elbow. 

In  Fig.  4 the  foot  is  leaving  by  its  inner  border.  In  Fig.  5 
the  olecranon  is  more  in  view,  since  it  is  turned  out,  at  the  same 
time  the  foot  is  now  everted  ( i.e .,  rotation  outward  has  taken  place 
as  the  limb  passes  from  impact  of  backward  strain  to  that  of  re- 
cover). Extreme  position  of  eversion  (Fig.  8)  is  coincident 
with  the  distance  between  the  olecranon  and  the  humerus,  and 
the  greatest  reduction  of  distance  between  humerus  and  anterior 
border  of  the  arm.  The  posterior  border  of  the  arm  is  here 
beginning  to  leave  the  side  of  the  trunk,  and  a white  light  is  re- 
flected from  over  the  triceps  muscle. 

During  the  forward  movements  of  Figs.  9 to  12  the  limb  is 
slowly  passing  back  to  the  position  where  the  olecranon  is  again 
in  line  with  the  posterior  border  of  the  limb  (i.e.,  strictly  speaking, 
in  profile  of  the  limb),  and  the  foot  is  preparing  for  a second 
period  of  impact  against  the  ground. 

The  lighter  shade  of  the  prominence  at  the  back  of  the  elbow 
answers  to  the  position  of  the  olecranon ; the  elongated  mass  of 
light  shade  which  extends  parallel  to  the  arm  between  the  elbow 
and  the  shoulder  answers  to  the  position  of  the  outer  border  of  the 
humerus.  It  is  evident  by  the  pictures  that  the  distance  between 
the  light  over  the  humerus  and  over  the  olecranon  is  variable. 
But  it  is  known  that  the  actual  distance  is  invariable,  and  there- 
fore the  apparent  variance  is  due  to  the  motion  of  the  limb  in 
rotation  at  the  shoulder,  by  which  the  region  of  the  back  of  the 
elbow  is  moved  somewhat  outward.  At  the  same  time  the  dis- 
tance from  the  outer  border  of  the  humerus  and  the  anterior 
contour  is  lessened  as  rotation  takes  place.  These  facts  being 


ANIMAL  LOCOMOTION. 


91 


borne  in  mind  the  following  additional  observations  can  be 
made : 

The  torsion  of  the  limb  is  pronounced  in  the  Tylopoda  ex- 
amined,— viz.,  the  camel,  the  dromedary,  and  the  guanaco.  This 
fact  should  not  be  disassociated  with  the  absence  of  anchylosis  be- 
tween the  cuboid  bone  and  scaphoid  bone  with  these  animals. 

In  contrasting  the  above  examples  with  the  Pecora, — e.g.y  the 
other  ruminants,  excepting  the  family  of  the  musk-deers,  not 
examined, — the  following  structural  features  may  be  mentioned 
as  correlations  of  peculiarities  of  gait. 

In  the  Tylopoda,  when  the  limb  is  supporting  the  body,  the 
hoof  is  always  in  line  of  support  with  the  rest  of  the  limb.  In 
the  deer  the  hoof  and  digits  are  angulated  with  the  rest  of  the  limb. 

In  the  Tylopoda  the  joints  are  thick,  and  the  outlines  are  dis- 
tinctly seen.  The  fore  limb  of  the  Tylopoda  is  never  noticed  at 
a point  posterior  to  the  withers,  but  leaves  the  ground  at  an  angle 
of  about  minus  forty  degrees.  The  fore  limb  of  the  Pecora  is 
vertical  at  a point  at  the  centre  of  the  trunk,  and  leaves  the 
ground  at  about  minus  fifteen  to  twenty  degrees.  When  the  limb 
is  off  the  ground,  the  digits  are  flexed  to  a greater  degree  in  the 
Tylopoda  than  in  the  Pecora. 

In  the  Pecora  the  limb  is  smaller  and  more  delicate  in  propor- 
tion to  the  bulk  of  the  body;  the  spread  of  the  hoof  is  less,  and 
the  movement  of  the  bones  each  in  the  other  more  precise  than 
in  the  Tylopoda. 

The  vertical  position  of  the  fore  limb  under  the  centre  of  the 
trunk  is  possible,  because  of  the  oblique  position  of  the  humerus. 
The  heavily-built  bovine  animals  present  the  same  contrasts  as 
the  deer,  with  the  exception  that  the  fore  limb  is  carried  less  back- 
ward. (See  p.  45.) 

The  camel  has  a relatively  short  metapodium.  The  joints 
present  curved  contours  in  place  of  angular  ones, — excepting  the 
angle  formed  by  the  hock, — and  even  this  is  less  pronounced  than 
in  other  ruminants. 


Minor  Peculiarities . 

While  the  general  features  of  the  quadrupedal  motion  are  in  all 
animals  the  same,  minor  peculiarities  of  the  carriage  have  doubt- 
less taxonomic  significance.  A number  of  these  will  be  indicated. 


92 


MATERIALS  FOR  A MEMOIR  ON 


The  dog  when  off  the  ground  flexes  the  fore  legs,  the  cat  ex- 
tends them.  This  probably  correlates  with  the  size  of  the  supra- 
spinous fossae  of  the  scapulae  in  the  two  animals.  (See  p.  84.) 

The  extended  fore  leg  in  the  cat  is  parallel  to  the  long  axis  of 
the  trunk,  while  in  all  the  ungulates  it  forms  an  angle  to  this  axis. 
The  angulation  of  the  parts  in  ungulates  is  subject  to  variation, 
being  more  open  in  the  deer  tribe  than  in  the  ox  ; in  a word,  in  the 
lighter-bodied  as  contrasted  with  the  heavy-bodied  forms.  The 
humerus  in  backward  movement  is  nearly  horizontal  in  the  Pecora. 
(See  pp.  42,  45.) 

The  enormous  size  of  the  anterior  dorsal  spines  in  the  hoofed 
animals,  their  smaller  size  in  the  claw-footed,  their  entire  absence 
in  Dipus  and  the  bat  (in  which  animals  the  fore  legs  are  not  used 
for  support),  the  trend  of  the  great  extrinsic  muscles  of  the  fore 
limb  towards  the  head,  all  prepare  the  observer  for  some  tax- 
onomic values  in  the  relations  existing  between  the  strength  of 
the  cephalo-humeral  muscles,  the  obliquity  of  the  fore  leg  in 
forward  movement,  and  the  size  of  the  anterior  dorsal  spines, 
and  possibly  in  the  shapes  of  the  atlas  and  axis. 

The  camel  protrudes  and  withdraws  the  under  lip  each  time 
the  fore  and  hind  limbs  are  shifted. 

In  the  North  American  buffalo  the  prepuce  is  drawn  backward 
when  the  hind  limbs  are  in  backward  strain. 

Characters  pertaining  to  the  Superficies  emphasized  in  the  Pho- 
tographs. 

It  is  a well-known  circumstance  that  the  photograph  will  bring 
out  details  of  structure  which  are  not  seen  by  the  unaided  eye. 
Thus,  an  inscription  on  a tombstone  which  was  covered  by  lichen 
and  was  quite  illegible  was  found  by  Professor  J.  T.  Rothrock  to 
be  read  with  the  greatest  ease  when  seen  photographed  after  the 
ordinary  manner.  The  photographs  of  the  series  of  animals 
studied  reveal  similar  interesting  features.  The  spots  on  the  lion 
and  the  lioness  are  much  more  distinct  than  they  are  in  the  living 
models.  In  the  lioness,  in  addition,  five  minute  points  are  detected 
on  the  back  of  the  trunk.  They  probably  correspond  to  the  em- 
inences of  the  skin  over  the  spines  of  the  dorsal  vertebrae. 

A fairly  recognizable  description  could  be  drawn  up  of  the 
superficial  muscles  of  the  limbs,  especially  of  those  fleshy  masses 


ANIMAL  LOCOMOTION. 


93 


which  pass  from  the  trunk  to  the  limbs.  The  reflections  of  light 
from  the  hair  of  the  figures  of  the  horse  may  be  ascribed  to  the 
changes  in  degrees  of  convexity  or  concavity  of  the  superficial 
muscle-masses,  while  some  of  the  stripes  of  the  tiger,  especially 
those  of  the  fore  limb  and  the  neck,  will  be  found  to  answer 
to  the  depressions  existing  between  well-defined  positions  of 
muscles  which  can  be  named  with  accuracy.  In  the  figures  of  the 
roan  horse  (series  582)  the  black  patch  on  the  rump  corresponds 
to  the  great  biceps  muscle. 

In  the  horse  (series  579)  the  depressions  between  the  muscles 
of  the  posterior  aspect  of  the  thigh  are  most  marked  when  the 
limb  is  in  the  first  stage  of  the  recover,  but  are  obliterated  when 
the  limb  is  in  backward  strain.  The  masses  at  the  inner  border  of 
the  thigh,  as  seen  in  the  horse  (series  582),  are  nearly  flat  when 
the  limb  is  off  the  ground,  but  conspicuously  convex  when  the 
animal  is  using  the  limb,  for  support. 

In  the  dog,  when  both  fore  feet  are  off  the  ground,  the  muscles 
which  pass  from  the  trunk  to  the  fore  limbs  are  exceedingly 
tense. 


On  the  Significance  of  the  Skin-Folds  on  the  Trunk  of  the  Hog. 

A number  of  minute  changes  in  the  contour  of  the  animals  are 
worth  noting.  In  the  figures  of  the  hog  (series  673  to  675),  at  the 
time  when  the  limbs  of  a single  side  are  the  nearest  one  to  the 
other  the  skin  is  observed  to  be  thrown  into  a series  of  vertical 
folds.  It  is  suggestive  of  the  mechanical  origin  of  the  bands  in 
the  armadillo  that  the  lines  in  the  hog  are  in  the  same  position 
as  the  bands.  They  appear  to  differ  only  in  the  circumstance 
that  the  folds  are  transient,  while  the  bands  are  permanent.  (See 
p.  45.) 

The  Mane. 

Each  time  the  horse,  in  the  series  590,  leaves  the  ground  by  one 
of  the  hind  feet  the  mane  streams  backward.  In  series  638,  as 
the  animal  descends  the  mane  streams  upward.  This  change  in 
position  is  caused  by  the  motions  of  the  head  and  neck  upward 
and  downward.  (See  especially  figures  of  the  horse  rocking,  series 
649  A.  See  p.  48.) 


94 


MATERIALS  FOR  A MEMOIR  ON 


The  Significance  of  the  Keel  on  the  Metapodium . 

The  presence  of  a ridge  on  the  distal  ends  of  the  bones  of  the 
tarsus  and  carpus,  as  well  as  on  the  first  and  second  rows  of  pha- 
langes, is  indicative  of  a precision  of  motion  in  the  joints  of 
which  it  constitutes  a part.  Such  ridges  are  known  as  keels,  and 
are  found  in  the  feet  of  the  ruminants,  excepting  the  group  of  the 
camels,  and  in  the  horse.  The  primitive  types  of  mammalian  life, 
as  has  been  pointed  out  by  Professor  E.  D.  Cope,*  were  without 
the  keel.  It  first  appeared  on  the  posterior  surface  of  the  articu- 
lar surface,  and  subsequently  upon  its  anterior  surface  as  well. 
These  facts  suggest  the  conclusion  that  the  ridge  was  developed 
for  some  exigencies  of  the  foot  while  in  backward  strain,  and  in 
the  action  of  the  transition  from  “on”  to  “off,”  since  the  keel 
first  appears  on  the  flexor  side  of  the  foot,  and  that,  since  in 
extant  animals  the  camel  and  its  kin  are  without  the  keel,  a 
careful  comparison  of  the  motions  in  these  creatures  with  those  of 
the  other  ruminants  would  be  suggestive  of  the  use  of  the  keel, 
and  lead  to  some  interesting  differences  between  the  gaits  of 
primitive  and  specialized  types. 

After  having  made  careful  studies  of  the  series  of  the  Egyptian 
camel  (736),  the  Bactrian  camel  (737  to  742),  and  the  guanaco 
(743),  I have  been  unable  to  find  any  features  which  correlate 
with  these  anatomical  peculiarities. 

Evolution  of  the  Gait. 

The  gait  in  its  various  expressions  is  based  upon  the  correla- 
tions between  the  fore  and  the  hind  limbs.  Assuming;  that  the 
simplest  movement  is  an  alternate  action  of  a single  pair  (syn- 
chiry),  the  simplest  gait  is  that  in  which  this  alternation  occurs 
in  each  pair  independently.  The  gallop  is  thus  the  simplest  gait, 
since  the  fore  pair  and  the  hind  pair  are  independent.  But  the 
gallop  depends  upon  a high  momentum,  and  we  must  assume 
that  the  primitive  animals  were  slow  walkers.  When  in  a slow 
rate  the  same  independence  is  observed, — i.e .,  when  the  right  fore 
foot  is  moved  forward  at  the  same  time  as  the  right  hind  foot 
(lateral  heterochiry), — the  two  pair  act  rhythmically,  and  the  feet 
“ keep  step.”  This  is  seen  in  the  rack,  which  thus  becomes  a 


* The  Origin  of  the  Fittest. 


ANIMAL  LOCOMOTION. 


95 


practicable  gait  for  a primitive  creature.  The  only  objection  to 
this  conclusion  is  the  fact  that  in  the  giraffe,  which  is  a specialized 
and  aberrant  form, — and  the  legs  are  remarkable  for  their  length, 
— we  have  the  best  example  of  a natural  pace. 

The  simplest  forms  of  moving  appendages  are  seen  in  the 
Nerita,  one  of  the  fresh-water  worms,  in  which  the  bristle-like 
rods  are  moved  in  all  directions  without  concert.  In  other  forms, 
as  in  the  sea-hare  (Aphrodite),  the  bristles  move  in  numerous 
lines  extending  alongside  of  the  body,  but  each  line  in  turn  being 
independent  of  those  adjacent  to  it.  The  next  arrangement  ob- 
tains in  myriapods,  whose  feet,  while  in  pairs,  are  seen  to  move 
as  the  horse’s  in  pacing, — i.e.,  each  row  acting  as  a whole,  and  the 
two  rows  alternating.  In  the  lower  crustaceans  the  same  method 
obtains.  In  the  higher  crustaceans,  as  in  the  crab,  the  two  parts 
of  a single  pair  may  act  together. 

It  stands  to  reason  that  when  to  one  side  of  the  body  a re- 
inforcement is  received  from  a limb  of  the  opposed  side  and  of  a 
different  pair  advancing  to  the  median  line,  a relatively  high 
degree  of  development  has  been  attained.  In  a phrase,  in  animals 
with  highly  developed  central  nervous  systems  the  bilateral  co- 
ordinations become  as  practicable  as  the  unilateral. 

The  question  of  the  manner  of  using  the  feet  in  progression  is 
also  likely  to  be  a subordinate  one  to  the  question  of  the  size  and 
the  bulk  of  the  body.  In  short-legged,  heavy  animals  of  slow 
movement,  the  support  of  the  centre  of  the  heavy  trunk  by  the 
diagonal  use  of  a fore  and  a hind  limb  was  probably  early  obtained. 
Nevertheless  the  Echidna,  a good  example  of  an  animal  possessing 
a large,  heavy  body  and  short  limbs,  walked  by  diagonal  hetero- 
chiry.*  The  feet,  however,  did  not  approach  each  other  towards 
the  centre  of  the  trunk,  as  is  the  case  in  the  walk  and  the  trot  of 
the  horse,  but  kept  to  the  side  of  the  body. 

In  long,  slender  natatorial  forms,  which  would  occasionally 
slide  among  the  ooze  of  a river-bed, — such  an  animal,  for  exam- 
ple, as  the  Potomogale, — doubtless  specialization  can  be  attained 
in  the  line  of  development  of  many  of  the  gaits. f We  have 


* This  was  observed  in  the  specimen  at  the  Zoological  Garden,  Philadelphia, 
f The  crocodile  of  the  Jumna,  according  to  Hornaday  (“Three  Years  in 
the  Jungle,”  1885,  p.  55),  can  stand  upon  the  legs  in  the  same  manner  as  a 
terrestrial  quadruped. 


96 


MATERIALS  FOR  A MEMOIR  ON 


seen  that  the  giraffe  uses  the  pace  for  all  rates  of  movement;  also 
that  the  horse  modifies  his  paces  by  the  character  of  the  ground 
he  traverses.  It  is  probable  in  like  manner  that  an  animal  will 
by  natural  selection  determine  his  methods  of  progression.  Marsh- 
dwellers  are  uniformly  of  the  heavy-bodied,  short-legged  type. 
In  an  animal  emerging  from  the  marsh  to  the  plains  the  limbs 
would  become  more  compact  and  longer  and  the  gait  more  various.* 
Catonf  states  that  the  Virginia  deer  bounds  up  once  or  twice  at 
the  beginning  of  his  gait,  to  observe  the  surrounding  country  be- 
fore he  settles  down  to  a steady  run.  This  habit  would  be  of  no 
use  in  an  animal  living  on  a prairie,  and  is  absent  in  the  mule- 
deer.  Mere  speed  is  not  a necessity  of  a change  of  gait.  A trot 
can  be  based  on  the  walk;  the  fast  pace  on  the  slow  pace.  In  the 
opinion  of  Dr.  M.  H.  Cryer,  a horse  in  going  over  a hurdle  em- 
ploys the  same  division  of  his  stride  as  in  the  run. 

Variability  of  gait  in  a single  animal  may  be  accepted  as  an 
evidence  of  high  development.  Diversity  of  function  in  the 
study  of  the  gait  is  of  the  same  value  as  in  other  subjects  of 
biology.  Thus,  an  animal  starting  a movement  on  the  laterals 
by  bringing  into  use  a member  of  the  opposite  side,  so  that  three 
feet  may  be  on  the  ground  at  the  same  time,  can  develop  a walk 
from  the  primitive  pace,  and  can  either  maintain  it  at  will  or, 
shifting  from  the  right  to  the  left  lateral  support,  show  a high 
degree  of  division  of  functional  labor  in  the  use  of  the  limb.  In 
like  manner,  when  an  animal  wishing  to  increase  his  rate  of  speed 
can  by  election  leave  the  walk  to  amble,  gallop,  trot,  or  pace,  an 
advantage  is  secured  over  another  animal  in  which  the  choice  is 
either  withheld  or  limited. 

Of  the  two  pairs  of  limbs,  the  front  one  is  the  more  adaptive 
for  the  reason  that  it  is  capable  of  so  many  secondary  modifica- 
tions, as  grasping,  flying,  etc.  We  may  assume  by  analogy  that 
the  fore  limbs  are  active  in  changing  gaits,  the  hind  limbs  acting 
in  a more  rigid  and  uncompromising  manner.  (See  p.  51.) 


* According  to  F.  C.  Selous,  Proc.  Zool.  Soc.  London,  1881,  p.  726,  Rhi- 
noceros simus  can  gallop.  , 

-j-  Antelope  and  Deer  of  North  America,  p.  270. 


ANIMAL  LOCOMOTION. 


97 


THE  MOVEMENTS  OF  THE  HUMAN  SUBJECT. 

The  motions  of  the  hands  and  feet  are  essentially  those  of  the 
quadruped.  In  the  series  258,  the  man  rising  from  a recumbent 
position  on  the  ground  first  uses  the  left  arm  for  support,  subse- 
quently transfers  the  weight  to  the  right,  and  after  gaining  the  up- 
right position  retains  the  hand  last  named  as  though  it  were  in 
the  first  stage  of  the  recover,  as  seen  in  the  foot  of  the  quadruped. 
The  dictum  made  in  connection  with  the  flexor  muscles  aiding  the 
foot  of  the  quadruped  to  maintain  itself  on  the  ground  is  here  ex- 
emplified (p.  42).  It  is  interesting  to  note  that  the  moment  the 
hand  leaves  the  ground  it  becomes  markedly  flexed. 

Gait. 

In  series  69  the  position  of  the  arms  (being  thrown  back  at  the 
time  that  the  hind  leg  of  the  opposed  side  is  also  thrown  back) 
sustains  the  assertion  that  the  motion  of  the  limbs  of  man  is  heter- 
ochiral.  The  chief  distinction  between  the  gait  of  man  and  that  of 
the  quadruped  is  the  degree  of  torsion  of  the  vertebral  column. 

For  a good  illustration  of  this  torsion  the  figure  of  the  boxer 
(series  333)  may  be  consulted. 

The  Action  of  the  Disengaged  Limb. 

In  series  311  and  312,  while  the  right  hand  is  engaged  in 
throwing  a weight  the  left  is  in  a state  of  great  tension.  The 
limb  is  extended  and  the  fingers  are  abducted.  The  fingers  remain 
extended  save  at  the  terminal  phalanges,  and  show  activity  of  the 
interossei  muscles.  The  position  just  named  is  suggestive  and 
presents  a raison  d’etre  for  the  following  reflections : 

First,  that  the  unemployed  arm  is  thrown  into  a state  of  ex- 
citement because  of  the  intentive  strain  on  groups  of  muscles  in 
close  co-ordination  with  them, — viz.,  the  muscles  of  the  limb  of 
the  opposed  side.  The  limb  cannot  repeat  the  exact  attitude  of  the 
one  in  use,  and  naturally  tends  to  take  on  the  form  of  the  primal 
limb.  This  form  is  that  of  a motion  as  though  it  were  on  the 
ground  and  serving  the  purposes  of  progression.  As  is  known 
from  the  study  of  the  quadruped,  the  limb  after  extension  passes 
gradually  into  flexion.  It  is  evident  that  the  interossei  muscles 
would  not  flex  the  terminal  phalanges  if  the  foot  were  on  the 

7 


98 


MATERIALS  FOR  A MEMOIR  ON 


ground,  but  would  simply  hold  the  ends  of  the  toes  firmly  to  the 
plane  on  which  the  animal  is  moving.  The  toes  are  also  markedly 
abducted  in  the  same  position.  The  attitude  taken  by  the  human 
fore  limb  is  precisely  that  of  the  fore  limb  of  the  quadruped  en- 
gaged in  terrestrial  progression,  and  is  modified  in  its  action  solely 
by  the  circumstance  that  it  “ claws  the  air.”  The  function  of  the 
interossei  would  appear  to  be  the  retention  of  the  phalanges  of  the 
terminal  row  against  the  ground  as  the  last  act  of  the  behavior  of 
the  foot  in  the  first  stage  of  the  recover. 

Second,  that  the  occurrence  of  convulsive  seizures,  in  which  the 
limb  assumes  the  position  just  described,  may  not  necessarily  be 
the  result  of  an  irritation  of  the  centres  which  control  the  co-or- 
dination, but  an  evidence  of  a profound  irritation  elsewhere  in  the 
economy.  This  phenomenon  properly  belongs  to  the  group  of 
influences  described  by  Drs.  Mitchell  and  Lewis.* 

To  a still  greater  extent  than  in  the  quadruped  the  superficial 
muscles  are  conspicuous.  It  is  of  interest  to  note  that  the  sartorius 
muscle  may  be  tense  even  when  the  foot  is  on  the  ground,  as  is 
observed  in  the  figure  of  a man  lifting  a weight  (series  322,  Fig. 
12).  In  various  attitudes  the  several  portions  of  the  trapezius 
muscle  are  contracted.  In  series  323,  Fig.  9,  in  the  figure  of 
a man  engaged  in  lifting  a dumb-bell,  the  upper  portion  of  the 
dorsal  division  of  the  muscle  is  enormously  enlarged. 


Oscillation. 

The  single  series  designed  to  illustrate  the  movements  of  the 
pelvis  in  walking  is  not  in  all  respects  satisfactory. 

Since  the  index  at  first  inclines  to  the  right  side,  which  corre- 
sponds to  the  limb  which  is  off  the  ground,  the  idea  is  at  once 
suggested  that  the  inclination  is  greatest  towards  the  side  not  bear- 
ing weight,  especially  when  it  is  noted  that,  the  index  is  vertical 
and  parallel  to  the  vertebral  column  when  the  legs  are  both  on 
the  ground.  But  when  the  left  foot  is  lifted  the  lever  remains  in 
the  vertical  position,  and  no  definite  conclusion  as  to  the  effect 
of  the  movements  of  the  limbs  on  the  oscillation  of  the  level  is 
determined. 


* Philadelphia  Medical  News,  1885,  vol.  xlviii.  p.  169. 


ANIMAL  LOCOMOTION. 


99 


FLIGHT. 

The  flight  of  the  bird  is  illustrated  in  series  755,  756,  757, 
pigeon;  758  to  762,  cockatoo;  763,  764,  hawk;  769.,  770,  eagle. 
The  following  conclusions  have  been  drawn  from  the  photo- 
graphs : 

The  wing  is  extended  upward  from  the  horizontal  position  by 
the  deltoid  and  latissimus  dorsi  muscles  to  a line  which  is  perpen- 
dicular to  the  body,  and  is  quickly  again  depressed  to  the  hori- 
zontal position  by  the  pectorals.  (See  p.  40.)  This  constitutes 
the  first  stage  of  the  “ stroke.” 

“ Recover”  is  initiated  by  an  inward  rotation  of  the  humerus, 
semiflexion  of  the  wing  at  the  elbow  (the  pinion  remaining  ex- 
tended and  directed  obliquely  downward  and  outward),  and  is  car- 
ried well  forward  to  a degree  sufficient,  when  seen  in  profile,  to 
conceal  the  head.  In  this  position  the  primaries  are  semi-rotated 
so  as  to  present  the  least  amount  of  surface  to  the  air  in  the  direc- 
tion in  which  the  bird  is  moving.  The  impetus  excited  by  the 
“ stroke”  carries  the  bird  upward  and  forward.  In  the  second 
stage  of  “ recover”  the  humerus  is  rotated  outward,  the  arm  is 
quickly  raised,  the  primaries  restored  to  the  position  seen  in  the 
bird  at  rest,  and  the  wing  is  a second  time  ready  for  the  “ stroke.” 
(See  p.  38.) 

In  the  eagle  and  the  hawk  the  legs  are  in  the  position  of  the 
“ stroke”  when  the  wings  are  similarly  placed.  During  the 
“ stroke”  the  legs  move  backward.  This  position  continues 
during  the  “ recover”  of  the  wing,  so  that  the  time  of  the  “ re- 
cover” is  also  that  of  the  “ recover”  of  the  leg. 

Biological  Department 
University  of  Pennsylvania, 

July  1,  1887. 


100 


MATERIALS  FOR  A MEMOIR  ON 


APPENDIX. 

A LIST  OF  THE  QUADRUPEDS  AND  BIRDS  REPRESENTED  IN 
THE  PHOTOGRAPHS, 

BY  EDWIN  A.  KELLEY. 


Series  563-657.  Horse — Equus  caballus,  Linn. 

“ 658-664.  Mule,  hybrid — E.  asinus  and  ^ E.  caballus. 

“ 665-668.  Ass — Equus  asinus,  Linn. 

“ 669-672.  Ox — Bos  taurus,  Linn. 

“ 673-675.  Sow — Sus  scrofa,  Linn. 

“ 676-679.  Goat — Capra  hircus,  Linn. 

“ 680.  Oryx — Oryx  leucoryx,  Pall. 

“ 681.  Virginia  Deer — Cariacus  virginianus,  Gm. 

“ 682.  Fallow  Deer — Dama  vulgaris,  Gray. 

“ 683.  Virginia  Deer — Cariacus  virginianus,  Gm. 

“ 684-691.  Fallow  Deer — Dama  vulgaris,  Gray. 

692-695.  Elk — Cervus  canadensis,  Schreb. 

696.  Eland — Oreas  canna,  H.  Smith. 

697-698.  Dorcas  Gazelle — Gazella  dorcas,  Linn. 

699-700.  American  Bison — Bison  americanus,  Gm. 
701-702.  White-tailed  Gnu — Connochaetes  gnu,  Zimm. 
703-715.  Dog — Canis  familiaris,  Linn. 

716-720.  Cat — Felis  domestica,  Bris. 

721-726.  Lion  cf — Felis  leo,  Linn. 

727-728.  Lion  C^—  “ “ 

729-730.  Tiger  — Felis  tigris,  Linn. 

731.  Jaguar — Felis  onca,  Linn. 

732-735.  Elephant — Eleplias  indicus,  Cuv. 

736.  Dromedary — Camelus  dromedarius,  Linn. 

737-742.  Bactrian  Camel — Camelus  bactrianus,  Linn. 
743.  Guanaco — Lama  huanacos,  Mol. 


ANIMAL  LOCOMOTION. 


101 


Series  744-745.  Raccoon — Procyon  lotor,  Linn. 

“ 746.  Capybara — Hydrochoerus  capybara,  Erxl. 

“ 747-749.  Chacma  Baboon — Cynocephalus  porcarius,  Bodd. 

“ 750.  Sloth — Cholcepus  hoffmani,  Peters. 

“ 751-754.  Kangaroo — Macropus  giganteus,  Shaw. 

“ 755-757.  Common  Pigeon — Columba  livia,  Bris.,  var.  domestica. 

“ 758-762.  Cockatoo — Cacatua  galerita,  Lath. 

“ 763.  Red-tailed  Hawk — Buteo  borealis,  Gm. 

“ 764.  Fish-Hawk — Pandion  haliaetus,  Linn,  var.  carolinensis,  Gm. 

“ 765-768.  Turkey- Vulture — Cathartes  aura,  Linn. 

“ 769-771.  American  Eagle — Haliaetus  leucocephalus,  Linn. 

“ 772-773.  Ostrich — Struthio  camelus,  Linn. 

“ 774-775.  Adjutant — Leptoptilus  argala,  Lath. 

“ 776-780.  Groups  of  birds,  as  follows : 

Muscovy  Duck — Cairina  moschata,  Linn. 

Canada  Goose — Branta  canadensis,  Linn. 

Blue  Goose — Anser  coerulescens,  Linn. 

Bar-headed  Goose — Anser  indicus,  Lath. 

Chinese  Goose — Anser  cygnoides,  Linn. 

European  (Mute)  Swan — Cygnus  olor,  Gm. 

American  Swan — Cygnus  americanus,  Sharpl. 

Black  Swan — Cygnus  atratus,  Lath. 

Sand-hill  Crane — Grus  canadensis,  Linn. 

Australian  Crane — Grus  australasiana,  Gould. 
Demoiselle  Crane — Anthropoides  virgo,  Linn. 
Crowned  Crane — Balearica  pavonina,  Linn. 

White  Stork — Ciconia  alba,  Bechst. 

Black  Stork — Ciconia  nigra,  Linn. 

Adjutant — Leptoptilus  argala,  Lath, 
etc. 

“ 781.  Chicken — Gallus  bankiva,  Temm.,  var.  domesticus. 


The  following  list  embraces  the  series  that  are  mentioned  by  number  in 
the  text  of  the  report : 


258 

576 

612 

633 

675 

695 

729 

747 

760 

311 

579 

616 

637 

677 

703 

730 

750 

761 

312 

581 

617 

641 

680 

704 

733 

755 

762 

322 

594 

619 

642 

681 

707 

743 

756 

763 

323 

595 

622 

649a 

682 

709 

744 

757 

764 

333 

601 

631 

658 

682a 

720 

745 

758 

769 

574 

602 

632 

670 

683 

728 

746 

759 

770 

A STUDY 


OF  SOME 

NORMAL  AND  ABNORMAL  MOVEMENTS 

PHOTOGRAPHED  BY  MUYBRIDGE. 

BY 

FRANCIS  X.  DERCUM,  M.D.,  Ph.D., 

INSTRUCTOR  IN  NERVOUS  DISEASES,  UNIVERSITY  OF  PENNSYLVANIA. 


In  the  following  study  the  writer  has  made  no  attempt  to  give 
a systematic  description  of  any  of  the  plates,  but  only  to  present 
the  salient  features  of  the  more  important  clinical  subjects  investi- 
gated. Naturally  these  subjects  are  of  greater  interest  to  neurol- 
ogists than  to  others.  The  normal  walk,  however,  possesses  an 
interest  that  is  general,  and  the  writer  believes  that  the  Muybridge 
method  has  in  this  field,  as  in  others,  yielded  new  results. 

In  addition  to  the  serial  photographs  which  have  been  pub- 
lished, Mr.  Muybridge  kindly  made,  upon  request,  a number  of 
clinical  photographs  by  means  of  a camera  armed  with  a fenes- 
trated wheel, — i.e.,  a Marey’s  wheel.  Some  of  these  pictures  are 
here  reproduced. 

Thanks  are  due  to  Drs.  S.  Weir  Mitchell,  William  Pepper,  H. 
C.  Wood,  Charles  K.  Mills,  and  James  H.  Lloyd  for  the  oppor- 
tunity of  photographing  various  patients  under  their  care. 

The  writer  desires  also  to  express  his  obligations  to  Mr.  Muy- 
bridge for  his  great  and  many  courtesies,  which  necessitated  not 
only  encroachment  upon  his  most  valuable  time,  but  also  the 
occasional  adoption  of  methods  not  included  in  his  original  enter- 
prise. 

Regarding  the  various  trajectories  depicted  in  this  monograph, 
it  is  of  course  not  claimed  that  they  are  absolutely  accurate,  but 
merely  as  close  an  approximation  to  the  truth  as  the  method  of 
research  permits. 


103 


104 


A STUDY  OF  SOME 


The  Normal  Walk . 

In  order  that  the  various  abnormal  gaits  should  be  properly 
understood,  a study  of  the  normal  walk  had  first  to  be  made.  In 
this  connection  it  is  hardly  necessary  to  refer  to  the  work  of  the 
Weber  brothers  nor  to  the  earlier  results  of  Marey  and  Carlet, 
for  they  are  already  the  common  property  of  schools  and  text- 
books. In  more  recent  years,,  as  is  well  known,  Marey  invoked 
the  aid  of  photography  to  enable  him  to  confirm  and  add  to  his 
original  results  obtained  by  the  graphic  method.  His  photo- 
graphs, however,  were  confined  simply  to  the  analysis  of  the  verti- 
cal and  forward  movements  of  various  points  of  the  body,  and 
they  gave  no  information  whatever  of  the  direction  or  extent  of 
the  lateral  sway.  Marey  was  well  aware  of  this,  and  by  a most 
ingenious  application  of  the  stereoscope  to  his  photographic  wheel 
he  endeavored  to  remedy  this  defect.  The  pictures  that  he  ob- 
tained are  exceedingly  interesting,  and  when  examined  stereoptic- 
ally  give  one  the  impression  of  an  undulating  white  band  extend- 
ing through  space,  the  undulations  being  in  three  directions, 
forward,  vertically,  and  laterally.  His  achievement  was  indeed  a 
brilliant  one,  and  yet  the  pictures  do  not  admit  of  a detailed  study 
of  the  carves. 

However,  the  method  invented  by  Muybridge,  of  making  simul- 
taneous serial  photographs  of  a moving  man  or  animal  from  two 
points  of  view  at  right  angles  with  one  another,  has  yielded  pic- 
tures furnishing  all  of  the  elements  necessary  to  determine  the 
various  paths  of  motion.  It  must,  however,  be  admitted  that 
while  by  this  method  the  lateral  sway  is  quite  definitely  ascer- 
tained, there  is  a slight  loss  in  the  accuracy  of  the  curve  of  the  ver- 
tical and  forward  movements,  and  this  arises  from  several  causes. 
In  the  first  place,  a possible  and  probable  source  of  error  is  slight 
irregularity  in  the  intervals  of  time  between  the  successive  photo- 
graphs of  a series.  No  one  would  pretend  that  the  same  accuracy 
as  regards  regularity  in  the  sequence  of  exposures  could  obtain  in 
a serial  battery  of  cameras  as  in  such  an  apparatus  as  used  by 
Marey,  in  which  the  sequence  of  exposures  was  determined  by  the 
fenestra  of  a revolving  wheel.  Notwithstanding,  repeated  chro- 
nographic  measurements  made  by  Muybridge  showed  the  irregu- 
larities of  these  intervals  to  be  exceedingly  small  even  for  very 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


105 


rapid  movements.  Therefore  in  a movement  relatively  so  slow 
as  the  walk  they  can  be  practically  discarded. 

Another  cause  for  slight  loss  of  accuracy  arises  from  the  fact 
that  the  person  walking  cannot  be  in  exact  apposition  with  the 
lateral  background  which  is  used  as  a scale.  This  error  is  of  course 
lessened  by  the  use  of  lenses  of  long  focus, — i.e , in  the  lateral  bat- 
tery of  cameras,  which  was  placed  upwards  of  fifty  feet  from  the 
track.  Being  by  this  means  so  much  diminished,  it  can  also  be 
discarded.  A third  source  of  inaccuracy  is  due  to  the  fact  that 
the  various  phases  of  any  movement  photographed  cannot  be,  ex- 
cept by  improbable  accident,  directly  in  front  of  the  centre  of 
each  corresponding  camera.  Therefore  each  individual  phase,  in- 
stead of  being  photographed  from  a position  exactly  at  right  angles 
to  the  background,  is  doubtless  in  the  majority  of  instances  photo- 
graphed at  an  angle  varying  slightly  from  the  right  angle.  Fur- 
thermore, for  the  various  phases,  this  angle  is  a variable  and  in- 
determinate quantity.  However,  it  must  again  be  insisted  that 
for  the  majority  of  movements,  especially  slow  movements,  such 
as  walking,  this  error  is  also  small,  though  it  is  obviously  greater 
than  the  second  error  just  mentioned. 

Taken  all  in  all,  while  the  serial  method  gives  slightly  less 
accurate  results  regarding  the  rise  and  fall  and  onward  move- 
ment of  a limb,  it  more  than  compensates  for  this  loss — which 
in  itself  is  slight — by  enabling  us  to  determine  the  amount  and 
direction  of  the  lateral  sway.  Furthermore,  apart  from  the  mere 
determination  of  trajectories,  two  photographs  of  any  one  phase 
of  movement  taken  at  right  angles  give  us  an  opportunity  for  the 
study  of  the  action  of  a part  which  a wheel-photograph  can  in  no 
way  furnish. 

Having  considered  the  various  sources  of  error,  let  us  take  up 
the  study  of  the  walk  in  Plate  1.  The  model  was  a young  man 
of  medium  height  and  was  photographed  while  taking  a long 
step. 

By  means  of  a transparent  scale  identical  with  that  of  the  back- 
ground, the  vertical  and  forward  movements  of  various  points  of 
the  body  were  readily  studied.  The  lateral  sway  was  determined 
by  means  of  a transparent  scale  based  upon  the  broad  divisions  ot‘ 
the  background  at  the  end  of  the  track, — that  is,  the  distance 
between  the  heavy  white  lines,  which  is  equivalent  to  thirty  centi- 


106 


A STUDY  OF  SOME 


metres,  was  taken  as  the  basis  of  the  scale ; but  for  greater  accu- 
racy this  distance  was  divided  into  ten  parts,  instead  of  into  six, 
as  in  the  original  background.  A plan  of  the  track  was  then 
made  (see  Diagram  1)  and  the  scale  corrected  for  the  error  in  per- 
spective for  the  area  in  which  the  step  was  taken.  In  Diagram  2, 

Fig.  1. 


c,  Eise  and  fall  and  forward  movement  of  right  hip  ; d,  Lateral  sway  of  hip. 

the  actual  size  of  the  track  and  the  normal  scale  are  in  red  lines, 
while  the  corrected  scale  is  in  black  lines.* 

It  should  have  been  stated  that  the  study  of  the  lateral  sway 
was  made  upon  the  middle  series  of  Plate  1,  as  here  the  images 
and  background  are  comparatively  sharp. 


* See  explanation  of  Diagrams. 


td 


EXPLANATION  OF  DIAGRAMS. 


In  the  following  explanation  the  words  “ lateral  scale”  are  used  to  designate 
the  divisions  of  the  background  opposite  the  lateral  battery  of  cameras.  The 
words  “terminal  scale”  are  used  to  designate  the  divisions  of  the  back- 
ground at  the  end  of  the  track. 

It  should  also  be  noted  that  in  making  the  study  of  the  lateral  sway,  the 
transparent  scale  was  for  convenience  so  applied  that  one  of  its  heavy  lines 
coincided  with  the  central  line  of  the  terminal  scale.  This  line  is  in  the 
centre  of  the  broad  division  occupying  the  middle  of  the  background.  The 
line  AB  of  Diagram  1 and  2 is,  therefore,  a projection  of  this  line  along  the 
course  of  the  track,  and  the  divisions  and  subdivisions  of  the  scale  are  pro- 
jected in  relation  with  this  central  line. 

DIAGRAM  1. 

The  line  AB  equals  the  length  of  the  track.  The  divisions  of  the  line  CD 
equal  the  divisions  of  the  terminal  background,  equivalent  to  thirty  centi- 
metres each.  B equals  the  position  of  the  upright  battery  of  cameras  by 
means  of  which  the  middle  series  of  pictures  of  Plate  1 of  Muybridge’s  pho- 
tographs were  made.  EPGH  equals  the  portion  of  the  track  on  which  the 
movement  photographed  was  made.  The  arrow  indicates  the  direction  in 
which  the  model  moved. 

DIAGRAM  2. 

The  portion  of  the  track  marked  EFGH  in  Diagram  1 is  in  Diagram  2 
represented  much  enlarged.  The  horizontal  red  lines  are  noticed  to  be  of 
two  kinds,  heavy  and  light.  Of  these  the  heavy  lines  represent  the  broad 
divisions  of  the  terminal  scale  projected  along  the  track.  They  are  thirty 
centimetres  apart.  In  the  original  scale  this  space  is  subdivided  into  six 
others  of  five  centimetres  each.  In  the  diagram,  however,  for  greater  ac- 
curacy it  is  subdivided  into  ten  parts  of  three  centimetres  each,  as  also  in 
the  transparent  scale  used  in  making  the  actual  study  on  the  photographs. 

The  vertical  lines  in  the  diagram  represent  the  vertical  divisions  of  the 
lateral  scale  projected  across  the  track.  They  are,  therefore,  five  centimetres 
apart. 

The  black  and  slightly  converging  lines  constitute  the  corrected  scale  upon 
which  the  measurements  made  on  the  photographs  are  registered  and  on 
which  the  curves  are  constructed.  The  method  by  means  of  which  this  scale 
is  determined  is  illustrated  in  Diagram  1. 

The  heavy  black  line  marked  f is  intended  to  show  the  extent  and  direc- 
tion of  the  lateral  sway  of  the  left  foot.  The  lines  b and  d are  intended  to 
show  the  same  elements  for  definite  points  on  the  head  and  hip  respectively. 

It  is  evident  that  the  direction  of  the  step  was  not  exactly  the  same  as  that 
of  the  track,  but  that  it  was  slightly  oblique. 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


107 


In  Fig.  1,  the  line  a rep- 
resents the  rise  and  fall  and 
onward  movement  of  the 
white  button  in  the  cap 
worn  by  the  subject,  while 
the  line  b represents  the 
amount  and  direction  of 
its  lateral  sway.  As  in 
the  trajectory  of  the  pubis 
determined  by  Marey,  the 
number  of  vertical  oscilla- 
tions appear  to  be  double 
those  which  take  place  in  a 
horizontal  direction. 

In  Fig.  2,  the  rise  and 
fall  of  the  right  superior 
spinous  process  of  the  ilium 
is  represented  in  the  line  c. 
It  is  similar  in  general 
course  to  the  line  a,  but 
the  amplitude  of  the  wave 
is  much  greater.  This 
increase  in  amplitude  is 
doubtless  in  part  due  to 
the  meagre  lateral  oscilla- 
tion of  the  ilium  during 
the  time  the  right  foot  is 
fixed  upon  the  ground.  In 
fact,  in  the  line  d the 
amount  of  curve  is  ex- 
ceedingly small, — i.e.y  dur- 
ing the  time  the  ilium  is 
describing  the  arc  xy  (line 
c). 

In  Fig.  3,  the  line  e rep- 
resents the  rise  and  fall 
and  forward  movement  of 
the  left  foot,  the  internal 
malleolus  being  taken  as  a 


108 


A STUDY  OF  SOME 


definite  point.  It  is  seen  at  a glance  that  this  curve  is  made  up 
of  a number  of  elements.  The  curve  from  Y to  S is  formed  by 
the  maleolus  sweeping  upward  on  an  arc  the  radius  of  which 
centres  in  the  ball  of  the  great  toe.  At  the  next  instant  the 
centre  of  rotation  is  transferred  to  the  tip  of  the  great  toe,  and 
a change  in  direction  is  noticed,  therefore,  at  the  point  S.  The 
balance  of  the  curve  up  to  the  point  Z is  the  result  of  the  flex- 
ion of  the  leg  and  of  the  forward  movement  of  the  pelvis ; thence 

Fig.  4. 


Tracing  and  trajectory  constructed  from  Plate  8.  The  trajectory  is 
supposed  to  pass  through  the  external  malleolus.  (Incomplete.) 

to  the  final  impact  of  the  heel  upon  the  ground  the  curve  is  the 
resultant  of  a complex  movement,  in  which  three  principal  ele- 
ments are  distinguishable:  first,  & pen- 
dulum movement , second,  a fall , and 
third,  a forward  movement , the  latter 
being  due  to  the  movement  forward 
of  the  body  as  a whole.  The  first  two 
elements  are  those  of  a cycloid,  and 

other  things  equal,  along  the  line  of 
swiftest  descent. 

A fourth  element  is  observed  in  the 
slight  secondary  rise  occurring  in  the  curve  just  previous  to  its 
termination.  The  significance  of  this  rise  is  as  follows.  We 


the  foot  therefore  falls  to  the  ground, 


Fig.  5. 


■HHH 


■unsmniLWiK^esHHH 

HiSBSiSSSglHiMB 


Left  foot,  Plate  8. 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


109 


notice  that  the  heel  of  the  passive  leg  in  swinging  forwards  in  its 
cycloid-like  descent  does  not  immediately  strike  the  ground,  but 
that  just  previous  to  the  impact  it  again  makes  a slight  ascent. 
This  is  shown  not  only  in  the  curve,  but  also  in  all  of  the  plates 
illustrating  the  normal  walk.  (See,  also,  Fig.  5.)  We  should  ob- 
serve at  the  same  time  that  the  rate  of  motion  is  not  by  any  means 
uniform.  It  is  relatively  slow  in  the  beginning,  but  steadily  in- 
creases in  velocity  until  the  step  is  almost  completed,  when  a slow- 
ing of  movement  again  takes  place.  This  slowing  of  movement 
is  coincident  with  the  secondary  rise.  The  impact  of  the  heel  upon 
the  ground  is  then  made  without  any  waste  of  force  and  with  a 
minimum  amount  of  jar.  When  in  addition  we  reflect  that  the 
heel  is  but  a portion  of  a moving  lever  and  that  the  muscles  at- 
tached to  this  lever  are  elastic,  we  realize  that  the  jar  of  impact 
is  indeed  reduced  to  a minimum. 

The  curves  of  the  lateral  sway  are  also  exceedingly  interest- 
ing. The  fact  that  the  lateral  sway  of  the  head  is  greater  than 
that  of  the  hip  is  exactly  in  keeping  with  what  we  should  expect 
on  a priori  grounds.  The  pelvis  is  relatively  fixed  and  not  nearly 
so  free  to  move  as  the  head  or  upper  portions  of  the  trunk,  and, 
secondly,  the  tilting  of  a column  is  naturally  exaggerated  at  its 
upper  and  free  end. 

The  lateral  sway  of  the  foot  again  presents  an  interesting  inter- 
pretation. Its  extent  is  less  than  most  of  us  would  have  expected 
to  find,  being  in  fact  very  small.  This  signifies  undoubtedly  that 
the  extent  of  the  lateral  sway  is,  other  things  equal,  always  the 
least  possible  consistent  with  the  working  of  the  limb ; because, 
first,  the  greater  the  lateral  sway  the  greater  the  loss  of  time  con- 
sumed in  again  bringing  the  foot  to  the  ground ; and,  secondly,  the 
greater  the  lateral  sway  of  the  foot  the  greater  the  lateral  sway  of 
the  body  as  a whole,  and  the  greater  the  loss  of  time  and  force  at 
the  expense  of  the  forward  movement. 

Finally,  taking  all  of  the  trajectories  together,  it  is  evident  that 
the  movements  in  the  three  directions,  forward,  vertically,  and  later- 
ally, are  correlated.  Secondly,  the  prime  object  of  the  walk  being 
movement  in  a forward  direction,  it  follows,  other  things  equal, 
that  the  greatest  economy  of  time  and  force  obtains  when  the 
vertical  and  lateral  movements  are  reduced  to  a minimum.  This 
is  apparently  the  case  in  the  normal  walk. 


110 


A STUDY  OF  SOME 


The  Gait  in  Locomotor  Ataxia. 

This  gait  was  studied  in  Plates  546,  549,  550,  554,  and  560. 
All  of  the  cases  photographed  were  typical  of  locomotor  ataxia. 
The  patient  upon  whom  the  trajectories  were  studied  is  the  one  of 
Plate  560.  His  history  is  briefly  as  follows: 

H.  P.,  aged  thirty-four,  a clerk  by  occupation,  first  noticed  that 
his  general  health  was  failing  in  the  fall  of  1883.  He  was  at 
first  treated  for  general  neurasthenia,  but  soon  developed  sciatic 
pains  and  gastric  crises.  These  last  were  very  severe.  He  then 
disappeared  from  observation  for  two  years.  When  he  again  re- 
turned he  was  markedly  ataxic,  both  in  the  arms  and  legs.  He 
had  parasthesia  of  the  soles  of  the  feet,  contracted  pupils,  loss  of 
the  patellar  reflex,  retardation  of  sensation,  etc. 

In  Fig.  6 is  represented  the  right  foot  from  the  time  of 
leaving  to  again  striking  the  ground.  It  needs  but  a superficial 
glance  to  show  that  it  differs  markedly  from  the  normal  foot  in 

Fig.  6. 


Locomotor  ataxia,  right  foot. 

its  course.  Compare,  for  instance,  Figs.  4 and  5.  It  differs  more 
widely  still  from  the  foot  seen  in  Fig.  9,  that  of  lateral  sclerosis. 

The  direction  and  extent  of  the  lateral  sway  was  determined 
by  means  of  a transparent  scale  corrected  for  perspective  for  each 
position  of  the  foot.  (See  Fig.  7.)  The  external  malleolus  is 
selected  as  a relatively  fixed  point.  The  curve  evolved  is  repre- 
sented in  line  a,  Fig.  8,  whilst  the  rise  and  fall  and  onward 
movement  are  shown  in  line  b. 

The  striking  difference  between  line  a and  the  corresponding 
curve  of  the  normal  gait  consists  in  its  irregular  and  extensive 
outward  sway,  while  in  the  line  b the  difference  consists  in  the 
increased  amplitude  of  the  curve  and  in  the  irregularity  of  the 


NORMAL  AND  ABNORMAL  MOVEMENTS.  Ill 


downward  fall.  Line  b is  made  up  of  the  same  elements  as  the 


Fig.  7. 


Eight  foot,  No.  1.  Eight  foot,  No.  2.  Eight  foot,  No.  3. 


Eight  foot,  No.  4. 


corresponding  line  of  the  normal  gait;  namely,  first,  a short 
curve  depending  upon  the  upward  rotation  of  the  malleolus  upon  a 

Fig.  8. 


Locomotor  ataxia,  right  foot. 

The  trajectories  are  supposed  to  pass  through  the  external  malleolus. 

radius  centring  in  the  ball  of  the  great  toe ; secondly,  a more  as- 

8 


112 


A STUDY  OF  SOME 


cending  curve  depending  upon  the  centre  of  rotation  being  trans- 
ferred to  the  tip  of  the  great  toe.  This  curve  passes  insensibly 
into  another,  caused  by  the  flexion  of  the  leg  upon  the  thigh  and 
by  the  onward  movement  of  the  hip.  It  is  to  be  noticed  that 
flexion  of  the  leg  is  much  more  marked  than  in  the  normal  con- 
dition ; consequently,  the  corresponding  portion  of  the  curve  is 
higher.  The  fall  of  the  foot  to  the  ground  we  noticed,  both 
in  line  b and  in  Fig.  6,  is  somewhat  irregular;  also,  that  the 
heel  fails  to  make  the  slight  ascent  which  occurs  in  the  normal 
walk  just  before  the  impact  on  the  ground;  and,  finally,  that 
when  the  impact  does  take  place  it  is  made  by  a sudden  descent 
or  fall. 

The  writer  does  not  by  any  means  desire  to  impress  the  reader 
as  though  these  curves  ( i.e .,  of  Fig.  8)  indicate  the  invariable 
paths  through  which  every  ataxic  must  move  his  feet.  He  does, 
however,  insist  that  the  two  principal  factors  indicated,  namely, 
the  increased  lateral  sway  and  the  increased  height  to  which 
the  foot  is  raised,  are  constant.  To  these  must  be  added  irregu- 
larity of  movement,  as  irregularity  is  itself  an  essential  feature 
of  ataxia.  An  interesting  confirmation  of  the  constancy  of 
these  factors  is  seen  in  Plate  550.  Here,  a Dane,  aged  fifty-two 
years,  with  a history  of  a long-standing  and  increasing  ataxia, 
was  first  photographed  (see  upper  series)  while  walking  with  the 
eyes  open.  An  examination  of  the  figures  shows  that  although 
the  gait  differs  from  the  normal  in  the  two  principal  factors  de- 
scribed, yet,  owing  to  the  guidance  afforded  by  his  eyes  and  to  the 
evident  effort  he  is  making,  as  shown  in  the  throwing  back  of  the 
shoulders  and  the  fixation  of  the  trunk,  his  walk  is  tolerably  good. 
In  the  lower  series,  however,  he  was  photographed  while  his  eyes 
were  closed.  A remarkable  change  is  at  once  observed,  and  it 
needs  no  elaborate  study  of  the  trajectories  to  show  what  the  chief 
elements  of  the  change  are.  It  is  seen  at  once  that  the  foot  is 
raised  much  higher  from  the  ground,  and  that  the  lateral  sway  is 
enormously  increased ; also,  that  the  successive  steps  are  more 
irregular.  In  this  series,  also,  the  abrupt  descent  of  the  foot  upon 
the  ground  is  again  noticed,  the  entire  sole  impinging  or  flopping, 
as  it  were,  upon  the  ground  at  once.  In  Plates  546  and  554,  which 
represent  cases  of  ataxia  more  or  less  advanced,  the  essential  points 
of  the  ataxic  gait  are  pronounced,  as  they  are  also  in  Plate  549. 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


113 


To  show  how  difficult  it  is  to  observe  a moving  limb,  even 
when  the  movement  is  slow,  it  need  only  be  stated  that  medical 
writers  almost  without  exception  describe  this  gait  erroneously. 
Almost  all  lay  stress  upon  rigidity  of  the  leg  and  insufficient 
action  of  the  knee-joint.  It  needs  but  a hasty  examination  of 
the  photographs  to  show  how  utterly  wrong  this  view  is.  Every 
one  of  the  plates  reveals  the  action  of  the  knee-joint,  and  in 
fact  of  all  of  the  joints,  to  be  far  in  excess  of  the  normal ; and, 
further,  the  rigidity  is  simulated  and  not  real.  Doubtless  this 
erroneous  view  has  its  origin  in  the  difficulty  of  separating 
mentally  the  active  from  the  passive  phase  of  the  leg.  Plate 
550,  which  is  one  of  the  most  instructive  in  the  collection,  ad- 
mirably suits  the  purpose  of  an  explanation.  It  is  seen  in  study- 
ing the  upper  lateral  series  that  the  passive  leg,  i.e.,  the  one 
suspended  in  the  air,  presents  exaggerated  knee-joint  action 
and  that  it  at  no  time  gives  even  the  semblance  of  rigidity.  The 
moment,  however,  that  it  impinges  on  the  ground,  i.e.,  the  mo- 
ments it  becomes  active,  all  action  at  the  knee  ceases.  More  than 
this,  as  the  weight  of  the  body  is  brought  upon  it,  the  extension 
becomes  absolute,  and  finally  the  knee  is,  so  to  speak,  locked ; that 
is,  recurved.  (This  is  well  seen  in  No.  6 of  the  series.)  By 
means  of  this  expedient  the  strain  is  thrown  upon  the  bones  and 
ligaments  of  the  joint  rather  than  trusted  to  the  treacherous 
muscles.  The  rigidity  is,  therefore,  not  muscular,  which,  in  fact, 
all  of  our  knowledge  of  ataxia  forbids.  How  much  voluntary 
effort  on  the  part  of  the  muscles  assists  in  steadying  the  limb,  of 
course  depends  upon  the  degree  to  which  the  disease  has  pro- 
gressed. 

Regarding  the  action  of  the  foot  and  the  manner  of  its  impact  on 
the  ground  various  accounts  have  been  given,  some  writers  main- 
taining that  the  heel  strikes  the  ground  first  and  considerably 
in  advance  of  the  plantar  surface,  and  others  maintaining  that  the 
entire  sole  strikes  the  ground  at  once.  An  examination  of  Plate 
550  shows  that  the  manner  of  impact  probably  depends  upon  the 
degree  of  the  ataxia.  In  the  upper  series,  in  which  the  patient 
was  photographed  while  having  the  guidance  afforded  by  his  eyes, 
the  heel  impinges  distinctly  before  the  sole,  while  in  the  lower 
series,  in  which  the  patient  walked  with  closed  eyes,  the  entire 
plantar  surface  impinged  at  the  same  time.  Occasionally  the 


114 


A STUDY  OF  SOME 


toes  came  down  first  and  sometimes  even  the  heels,  so  that  in  ad- 
vanced ataxia  any  part  of  the  foot  may  strike  the  ground  first. 

Regarding  the  lateral  sway  of  the  trunk,  it  needs  no  detailed 
study  to  tell  us  that  it  is  much  exaggerated.  In  ataxies  who  are 
still  able  to  walk  comparatively  well  this  exaggerated  sway  is  al- 
ways towards  the  side  opposite  the  advancing  or  passive  leg.  How- 
ever, if  the  ataxia  be  increased,  as,  for  instance,  in  the  lower 
series  of  Plate  550,  the  sway  may  be  towards  the  same  side,  and 
then  the  patient  is  in  danger  of  falling. 

The  Gait  in  Lateral  Sclerosis. 

This  gait  was  studied  in  Plate  548.  The  subject  was  a patient 
of  the  University  Hospital  and  was  under  the  care  of  Dr.  Wil- 
liam Pepper.  His  history  was  as  follows  :* 

u H.  S.,  aged  twenty-eight  years,  single,  is  an  engineer  by  oc- 
cupation, and  had  been  working  on  a railroad  in  Wyoming  Ter- 
ritory until  three  or  four  months  ago,  when  he  came  to  this  city. 
When  a child  he  had  diphtheria,  which  was  followed  by  dropsy 
and  paralysis.  Later  he  was  thrown  on  a hot  stove  and  severely 
burned,  the  scar  being  visible  on  the  epigastrium.  When  twenty- 
two  years  of  age  he  had  typhoid  fever.  He  denies  having  had 
gonorrhoea  or  syphilis,  although  intercourse  with  loose  women  is 
acknowledged.  Careful  investigation  fails  to  reveal  any  trace  of 
specific  infection.  He  has  used  alcohol  in  considerable  quantities, 
but  has  never  been  intoxicated.  He  uses  tobacco  in  great  excess, 
smoking  as  many  as  fifteen  cigars  on  some  days,  and  chewing  a 
large  plug  of  tobacco  every  twenty- four  hours. 

“ His  occupation  has  been  an  exposing  one,  subjecting  him  to 
extreme  alternations  of  heat  and  cold.  He,  however,  continued  in 
good  health  until  three  years  ago.  In  December,  1882,  he  first 
noticed  a gradual  loss  of  power  in  the  left  ankle.  He  states  that 
five  months  prior  to  this  he  had  injured  the  left  ankle  and  knee 
by  falling  from  his  locomotive.  This  kept  him  in  bed  for  seven 
days,  then  apparently  he  became  entirely  well.  The  feeling  of 
weakness  on  the  left  side  compelled  him  to  throw  most  of  his 
weight  on  the  right  leg.  The  trouble  gradually  grew  worse,  and 
in  November,  1883,  he  noticed  that  occasionally  the  affected  leg 

* See  Philadelphia  Medical  Times,  October  31,  1835.  Clinical  Lecture  by 
Professor  Pepper. 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


115 


would  suddenly  fly  backward  when  he  attempted  to  move  it,  and 
that  the  muscles  of  the  left  side  would  tremble  violently  in  quick 
clonic  spasm.  Unless  he  moved  very  carefully  this  occurred  at 
every  step.  He  next  observed  that  he  was  losing  flesh.  His 
height  is  six  feet  one  and  one-half  inches,  and  his  best  weight 
has  been  one  hundred  and  seventy-nine  pounds.  Three  months 
ago,  when  this  note  was  made,  he  weighed  one  hundred  and 
sixty-five  pounds. 

“ In  July,  1884,  the  affected  ankle  was  strained,  and  this  was 
followed  by  swelling  of  the  foot  and  leg. 

u About  this  time,  or  a little  earlier,  he  noticed  that  the  fingers 
of  the  left  hand  were  disposed  to  contract,  so  that  the  hand  would 
remain  closed  until  the  fingers  were  forcibly  extended.  The 
contraction  was  increased  by  fatigue.  This  gradually  increased 
until  it  involved  the  hand,  forearm,  arm,  and  shoulder.” 

At  the  time  at  which  the  photograph  was  taken,  the  summer 
of  1885,  the  patient  presented  in  addition  the  following  symp- 
toms : He  habitually  carried  the  left  arm  ( vide  Plate  548)  in  the 
semi-flexed  position  assumed  by  patients  having  lateral  sclerosis 
or  secondary  degeneration  of  the  lateral  columns.  The  left  leg 
was  decidedly  stiff.  When  sitting  on  a chair  it  was  extended.  The 
knee-jerk  was  markedly  exaggerated.  The  gait  was  “ spastic.” 
The  right  leg  also  was  somewhat  affected.  It  was  somewhat  re- 
sistant to  flexion  and  the  knee-jerk  was  evidently  increased. 

Fig.  9. 


The  gait  was  studied  in  detail  in  the  lower  series  of  Plate  548. 
Fig.  9,  as  well  as  the  lateral  series  in  the  plate,  shows,  in  the  first 
place,  that  the  left  foot  scarcely  left  the  ground,  that  the  heel  only 
was  elevated,  and  that  the  ball  of  the  foot  and  the  toes  were 
merely  raised  sufficiently  to  permit  them  to  slip  or  scrape  along 
the  surface ; also  that  the  leg  as  a whole  was  very  little  flexed. 


Lateral  sclerosis,  left  foot. 


Fig.  10. 


116 


A STUDY  OF  SOME 


Fig.  11. 


Lett  foot,  No.  5.  Left  foot,  No.  6. 


Left  foot,  No.  7.  Left  foot,  Nos.  8-12. 


Left  Foot. 


The  scale  is  in  each  instance  corrected  for  perspective.  From  7 to  12  there  is  absolutely  no  lat- 
eral sway,  as  the  foot  is  fixed  firmly  on  the  ground.  The  curved  line  represents  the  external  out- 
line of  the  leg  and  foot.  The  point  A,  No.  1,  shows  the  position  of  the  malleolus. 


Right  foot,  Nos.  1-7. 


Fig.  12. 


Right  foot,  No.  8. 


Right  foot,  No.  11. 

Eight  Foot. 


Right  foot,  No.  9. 


As  in  Fig.  10,  each  scale  is  corrected  for  perspective.  From  1 to  7 there  is  no  variation,  and  from 
8 to  12  the  variation  is  comparatively  small.  The  external  malleolus  was  as  before  the  point  on 
which  the  study  of  the  trajectory  was  based. 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


117 


In  the  other  leg  the  spastic  condition,  though  present,  was  not 
so  much  marked.  (See  Fig.  10.)  It  is  here  noticed  that  the  foot  is 
raised  clearly  off  the  ground,  and  that  the  leg  is  flexed,  and  yet 
neither  of  these  factors  is  as  marked  as  we  find  it  in  the  normal 
condition. 

The  trajectories  were  determined,  and  are  represented  in  Figs. 
13  and  14. 

The  amount  and  direction  of  the  lateral  sway  of  each  foot  was 
determined  by  the  use  of  a transparent  scale  corrected  for  per- 
spective for  each  position  of  the  foot.  The  external  malleolus  was 
the  point  used  in  making  each  measurement.  (See  Fig.  11,  Nos. 
1 to  12,  and  Fig.  12,  Nos.  1 to  12.) 

Fro.  13. 


Lateral  sclerosis,  left  foot. 

Rise  and  fall  (line  a)  and  lateral  sway  (line  b)  of  left  foot. 

In  Fig.  13  the  upper  line,  a,  shows  the  rise  and  fall  and  onward 
movement  of  the  foot,  whilst  the  lower  line,  6,  shows  the  amount 
and  direction  of  the  lateral  sway. 


Fro.  14. 


(■(1 

iSSiSSSSSSSS  ■! 

mmmm 

8Ei 

Hi 

suni 

Illiilllllll  ii 

laae 

in 

Lateral  sclerosis,  right  foot. 

Rise  and  fall  (line  c)  and  lateral  sway  (line  d)  of  right  foot. 


In  Fig.  14  the  lines  c and  d represent  the  same  factors  of  the 
right  foot.  It  is  noticed  in  the  left  foot  that  the  rise  and  fall  as 
well  as  the  lateral  sway  are  very  small.  It  will  be  remembered 
that  the  left  leg  was  the  one  most  diseased.  It  was  typically 


118 


A STUDY  OF  SOME 


affected.  In  Fig.  14  the  rise  and  fall  are  more  marked,  and  this 
again  is  in  harmony  with  the  fact  that  the  right  leg  was  much  less 
affected  than  the  left.  On  comparison,  however,  with  the  rise  and 
fall  of  the  normal  leg  (see  Fig.  5),  these  factors  are  seen  to  be 
much  less  pronounced. 

Again,  the  left  foot  at  the  completion  of  its  movement  is  brought 
too  far  within  the  median  line,  and  thus  gets  in  the  way  of  the 
right  foot.  The  latter  in  order  to  prevent  a fall  is  brought  too  far 
outside  of  the  median  line,  and  thus  the  direction  of  the  walk  as 
a whole  is  changed. 

As  regards  the  lateral  sway  of  the  trunk,  it  is  of  course  grossly 
exaggerated,  and  always  takes  place  towards  the  side  opposite  the 
advancing  leg.  It  is,  in  fact,  only  by  means  of  this  grossly  ex- 
aggerated sway  that  the  leg  can  be  advanced  at  all ; the  sway  tilts 
the  pelvis  and  thus  assists  in  raising  the  limb  from  the  ground. 

As  regards  the  relative  extent  of  the  lateral  movement  of  the 
trunk,  it  is  always  greater  towards  the  side  of  the  less  affected 
limb. 

The  gait  in  lateral  sclerosis  is  so  very  slow  that  medical  writers 
have  in  general  given  accurate  descriptions  of  it,  though  the  ex- 
tent of  the  lateral  sway  of  the  foot  is  too  much  insisted  on.  In 
all  probability  the  lateral  sway  is  never  very  marked  when  both 
legs  are  affected  or  affected  about  equally.  It,  however,  becomes 
much  exaggerated,  as  we  shall  see  below,  when  the  disease  is  con- 
fined to  the  lateral  column  of  one  side. 

Various  other  Spastic  Gaits. 

In  Plate  553,  are  presented  the  photographs  of  an  interesting  case, 
the  history  of  which  is  briefly  as  follows  : C.  M.,  aged  twenty-four, 
a laborer,  sixteen  months  ago  fell  into  a pit  eight  feet  deep,  striking 
on  the  top  of  his  head  ; he  was  unconscious  for  four  hours,  and  ex- 
perienced upon  awakening  a severe  pain  in  the  back  of  the  neck 
which  increased  upon  motion.  He  had  absolute  paralysis  of  both 
legs  for  six  weeks,  and  of  the  bladder  and  rectum  for  four  weeks. 
The  arms,  especially  in  the  act  of  flexion,  were  markedly  paretic. 
He  did  not  regain  the  power  of  walking  for  nine  weeks.  He 
had  improved  to  a certain  degree,  but  failed  to  progress.  At  the 
time  of  being  photographed  the  pupils  were  slightly  unequal, 
the  right  being  the  larger.  No  affection  of  special  senses  except 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


119 


impairment  of  hearing  in  right  ear  was  noted.  No  ansesthesia  ex- 
isted anywhere.  The  legs  were  paretic  and  spastic.  No  specific 
history  could  be  elicited. 

The  spastic  condition  of  the  legs  is  well  seen  in  the  photographs, 
though  the  gait  is  by  no  means  a typical  spastic  gait,  such  as  seen 
in  Plate  548  (lateral  sclerosis).  The  feet  are  raised  but  little  from 
the  ground,  and  appear  to  slide  along  the  surface.  The  lateral 
sway,  though,  is  greater  than  in  typical  disease  of  the  lateral 
columns.  In  the  latter,  the  meagre  outward  movement  of  the 
foot  is  brought  about  by  a forced  and  extreme  swaying  of  the 
trunk,  and  not  by  the  action  of  the  leg  itself. 

In  Fig.  543  is  found  another  illustration  of  an  atypical  spastic 
gait.  The  subject  was  an  hysterical  girl. 

It  is  seen  by  even  a cursory  examination  that  the  feet,  though 
not  raised  to  the  normal  height  above  the  ground,  are  yet  raised 
to  a height  greater  than  that  seen  in  typical  lateral  sclerosis. 
The  amount  of  the  lateral  sway,  too,  is  also  relatively  large. 
There  is  some  tendency  to  scrape  the  feet  along  the  ground,  espe- 
cially the  right  one,  but  there  is  a decided  outward  movement. 

Other  instances  of  spastic  gait  are  seen  in  Plates  547  and  552. 
Both  subjects  were  old  hemiplegics  with  marked  secondary  con- 
tracture. In  both  instances  the  paralyzed  leg  is  quite  stiff,  little 
or  no  flexion  taking  place  at  the  knee.  It  is  also  noticed  that  the 
foot  is  here,  almost  or  quite,  raised  from  the  ground  by  the  en- 
ormous swaying  of  the  trunk  towards  the  sound  side,  to  which 
additional  support  is  given  to  receive  the  sway  by  means  of  the 
crutch.  It  is  significant,  therefore,  that  the  crutch  be  carried  on 
the  sound  side.  In  these  figures  is  also  seen,  precisely  as  in  typical 
lateral  sclerosis,  the  exaggeration  of  the  normal  tendency  of  bring- 
ing the  outer  edge  of  the  foot  to  the  ground  in  advance  of  the  sole. 
This  is  especially  shown  in  the  lower  series  of  Plate  552. 

These  instances  of  what  might  be  called  unilateral  sclerosis 
differ,  therefore,  from  double  lateral  sclerosis  chiefly  in  the  great 
exaggeration  of  the  lateral  sway. 

In  Plate  542  still  another  example  of  spastic  gait  is  found,  but 
it  is  not  typical.  The  history  of  the  case  in  brief  is  as  follows : 
J.  C.,  female,  aged  forty-one,  commenced  to  have  pain  in  the 
back  some  fourteen  years  ago.  The  pain  has  steadily  continued. 
Soon  after  its  commencement  she  noticed  some  difficulty  in  walk- 


120 


A STUDY  OF  SOME 


ing.  The  legs  “ seemed  to  get  stiff  and  to  tremble.”  Afterwards 
jerking  of  the  hands,  arms,  shoulders,  and  head  commenced. 
This  jerking,  or  chorea,  is  still  present,  though  less  marked  than 
before.  She  has,  however,  a choreic  or  spasmodic  affection  of  the 
muscles  of  respiration  and  phonation,  as  her  breathing  and  her 
speech  are  very  irregular.  Her  speech  is  not  infrequently  in- 
terrupted by  a sudden  gush  of  inspiration,  which  produces  an 
ascending  note.  She  has  no  chorea  of  the  legs,  but  her  gait  is 
markedly  spastic,  and  she  walks  with  great  difficulty.  Her 
face,  too,  is  somewhat  choreic,  and  her  tongue  deviates  slightly  to 
the  left. 

The  case  was  doubtless  one  of  disseminated  sclerosis  in  which 
the  lateral  columns  were  markedly  affected. 

An  examination  of  the  plate  shows  that  she  barely,  if  at  all, 
raises  the  feet  from  the  ground.  The  amount  of  lateral  sway,  too, 
is  small,  and  her  steps  are  exceedingly  short. 

In  Plate  541  is  seen  the  walk  of  an  extremely  choreic  girl, — a 
chorea  which  had  lasted  from  early  infancy  and  appeared  to  be  of 
organic  origin,  probably  a disseminated  sclerosis.  It  is  therefore 
allied  somewhat  to  the  preceding  case.  At  first  the  gait  appears 
spastic.  However,  the  leg  which  is  at  one  instant  rigid  and  ex- 
tended is  at  the  next  instant  flexed.  It  is  interesting  to  note  the 
spastic  condition  of  the  right  arm,  which,  during  the  step,  is  rigidly 
extended  along  the  side  of  the  body.  The  head  and  neck  and 
even  the  toes  are  violently  contorted.  Of  course  in  such  a case 
no  two  steps  could  be  alike,  and  the  gait  could  only  be  termed 
irregular. 

Other  Abnormal  Gaits . 

In  Plate  551  is  represented  an  epileptic  suffering  from  a 
spastic  hemiplegia  which  is  more  pronounced  in  the  arm  than  in 
the  leg,  and  which  dates  from  early  childhood.  The  gait  is  in 
some  respects  a spastic  gait. 

Somewhat  similar  to  it  is  the  gait,  seen  in  Plate  561,  of  a 
rachitic  and  hydrocephalic  subject.  Here  both  legs  are  decidedly 
spastic. 

In  Plate  559  we  have  an  instance  of  partial  paraplegia.  The 
subject  was  a druggist  in  a country  town,  who  had,  several  years 
before,  been  thrown  from  a horse  and  had  received  a severe  con- 
tusion of  the  back.  He  gradually  lost  power  in  his  legs  until 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


121 


almost  unable  to  walk.  Syphilis,  though  denied,  was  suspected 
as  a concomitant  factor,  and  the  man  made  marked  improvement 
under  large  doses  of  potassium  iodide. 

It  is  to  be  noticed  that  the  feet  are  thrown  forward  in  a passive 
or  pendulum-like  manner,  and  that  the  weight  is  not  trusted  to  a 
leg  until  it  has  been  locked, — i.e.,  until  the  knee  has  been  thrown 
far  backward  (incurved), — so  that  collapse  from  sudden  flexion 
becomes  impossible. 

In  Plate  555  is  seen  the  gait  of  a case  of  monoplegia.  The 
monoplegia  is  due  to  a commencing  muscular  atrophy  affecting 
the  left  thigh  and  leg.  It  is  seen  that  the  diseased  leg  is  thrown 
forward  (see  lower  series)  in  the  same  helpless  or  pendulum-like 
manner  as  in  the  case  of  paraplegia;  also  (see  upper  series)  that 
the  weight  of  the  body  is  not  thrown  upon  it  until  the  knee  has 
been  well  locked.  This  is  in  marked  contrast  with  the  action  of 
the  normal  limb.  (See  plates  of  normal  walk.) 

Again,  the  strange  gait  of  Plate  558  is  worthy  of  a word. 
It  is  that  of  a case  of  stuporous  melancholia.  His  history  is 
as  follows.  He  is  twenty- five  years  old.  For  thirteen  years  he 
worked  as  a type-finisher,  being  constantly  exposed  to  fine  particles 
of  dust  mixed  with  lead.  Three  years  ago  he  had  an  attack  of 
acute  lead -poisoning,  with  marked  wrist-drop.  A year  later  he 
had  a period  of  excitement,  with  evidences  of  insanity.  He  then 
had  hallucinations  of  sight  and  hearing,  and  had  delusions  of  per- 
secution ; thought  his  sister  was  trying  to  poison  him,  and  that  his 
fellow-wTorkmen  were  constantly  endeavoring  to  have  him  dis- 
charged. After  being  in  this  condition  for  about  six  weeks,  he 
became  sullen  and  stuporous ; he  would  make  no  effort  for  him- 
self; had  to  be  fed  and  had  to  have  all  of  his  wants  attended  to 
by  his  friends.  His  stuporous  condition  largely  persists.  He 
does  not  speak  and  is  apt  to  remain  in  positions  in  which  he  is 
placed.  His  gait  might  be  described  as  a crouching  shuffle.  It 
is  certainly  in  keeping  with  his  mental  condition. 

Another  remarkable  gait  is  that  of  a case  of  infantile  paralysis, 
which  is  depicted  in  Plate  539,  and  in  which  the  child  has 
adopted  the  method  of  walking  on  all  fours.  The  foot-falls,  so 
to  speak,  occur  in  the  same  order  of  succession  as  they  do  in  the 
walk  of  a quadruped.  The  case  was  under  the  care  of  Hr.  James 
H.  Lloyd,  of  the  University. 


122 


A STUDY  OF  SOME 


Artificially -Induced  Convulsions . Plates  544  and  545. 

In  order  that  these  plates  may  be  understood,  it  will  be  neces- 
sary to  quote  from  the  paper*  in  which  these  convulsions  were 
first  described. 

“Our  experiments  were  performed  by  subjecting  a group  of 
muscles  to  a constant  and  precise  effort,  the  attention  being  at  the 
same  time  concentrated  upon  some  train  of  thought.  The  position 
we  most  frequently  adopted  was  the  following : The  subject  being 
seated,  the  tips  of  the  fingers  of  one  or  both  hands  were  so  placed 
upon  the  surface  of  a table  as  to  give  merely  a delicate  sense  of 
contact, — i.e .,  the  fingers  were  not  allowed  to  rest  upon  the  table, 
but  were  maintained  by  a constant  muscular  effort  barely  in  contact 
with  it.  Any  other  position  involving  a like  effort  of  constant 
muscular  adjustment  was  found  to  be  equally  efficient.  Any  one 
object  in  the  room  was  now  selected  and  the  mind  fixed  upon  it,  or 
some  subject  of  thought  was  taken  up  and  unswervingly  followed. 

“After  the  lapse  of  a variable  period  of  time,  extending  from 
a few  minutes  to  an  hour,  . . . tremors  commenced  in  the  hands. 
These  tremors  became  rapidly  magnified  into  rapid  movements  of 
great  extent,  sometimes  to  and  fro,  sometimes  irregular.  If  the 
experiment  was  now  continued,  the  muscles  of  the  arms,  shoulders, 
back,  buttock,  and  legs  became  successively  affected,  and  the  sub- 
ject was  frequently  thrown  violently  to  the  ground  in  a strong 
general  convulsion. 

“Seizures  equalling  in  violence  a general  convulsion  were  by 
no  means  induced  in  all  subjects,  and  were  generally  the  result  of 
experiments  repeated  many  times  during  the  same  evening.” 

The  subject  employed  in  the  experiments  from  which  the  photo- 
graphs were  made  was  a professional  artist’s  model,  a woman,  aged 
thirty-five,  of  indifferent  or  phlegmatic  temperament.  The  con- 
ditions of  the  experiment  were  much  less  favorable,  of  course, 
than  they  would  have  been  in  a private  room.  They  were  per- 
formed in  the  large  open  photographic  yard  and  amid  the  dis- 
tracting circumstances  of  strange  and  unusual  preparation.  How- 

*“  On  the  Artificial  Induction  of  Convulsive  Seizures, ” by  F.  X.  Dercum, 
M.D.,  and  A.  J.  Parker,  M.D.  : Journal  of  Nervous  and  Mental  Disease, 
vol.  xi.,  No.  4,  October,  1884 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


123 


ever,  as  both  the  plates  and  figures  show,  the  results  were  by  no 
means  unsatisfactory. 

In  Fig.  15  the  position 
of  the  subject  and  the  early 
stages  of  an  induced  convul- 
sion are  shown.  The  figure 
is  the  result  of  a number  of 
tracings  of  the  serial  photo- 
graphs of  Plate  545,  lower 
series,  being  superimposed. 

The  tremor  is  just  being 
magnified  into  to-and-fro 
movements  of  the  hands  and 
feet.  A photograph  of  this 
stage  was  also  made  by 
means  of  a “ Marey  wheel,” 
and  is  shown  in  Fig.  16. 

The  blurring  of  the  hands  and  feet  here  show  the  extent  of  the 
convulsion. 

Fig.  17  is  the  result  of  superimposed  tracings  of  the  upper 
series  of  pictures  in  Plate  545.  In  this  instance  the  subject  was 

simply  seated  on  a chair  facing 
the  cameras.  There  was  no 
table  used.  The  model  had 
already  induced  a number  of 
convulsions,  and  was  now 
asked  to  induce  a convulsion 
by  keeping  the  fingers  in  deli- 
cate contact  with  the  thighs. 
In  a short  time,  as  shown  by 
the  figure,  a most  violent  con- 
vulsion was  the  result. 

The  individual  pictures  of 
this  series  are  especially  inter- 
esting. The  entire  pose  or  attitude  assumed  by  the  subject  is, 
so  to  speak,  hysteroidal , while  the  purposeless  movements  of  the 
limbs  suggest  those  of  chorea,  than  which,  however,  they  are 
infinitely  more  rapid. 

In  Fig.  18,  which  is  the  result  of  a superimposed  tracing  of 


Fig.  16. 


124 


A STUDY  OF  SOME 


the  first  series  of  Plate  544,  the  subject  was  lying  upon  a mattress, 

and  the  convulsion  was  induced  by 
simply  attempting  to  keep  the  hands 
in  delicate  contact  with  the  body. 
The  convulsion,  as  shown  by  the 
figure,  was  of  considerable  violence. 

It  might  have  been  possible  by 
prolonging  the  experiment  to  pro- 
duce still  more  startling  results,  but 
the  unfavorable  surroundings,  the 
temperament  of  the  subject,  and  the 
fact  of  her  being  much  exhausted, 
forbade,  as  being  both  impracticable 
and  unjustifiable,  any  further  attempt. 

The  reader  may  appreciate  more 
fully  the  violence  of  these  seizures 
when  told  that  of  the  various  figures 
here  given,  each  represents  only  a brief  portion  of  a convulsion, 


Fig.  18. 


and  that  portion  embraced  within  so  small  an  interval  of  time  as 
1.8  seconds.* 

Case  of  Functional  Spasm.  ( Local  Chorea.)  Plates  556  and  557. 

This  remarkable  case,  some  of  the  phenomena  of  which  resem- 
ble those  seen  in  the  artificially  induced  convulsions,  was  first 
studied  by  Dr.  S.  Weir  Mitchell,  and  reported  by  him,  in  the 
American  Journal  of  the  Medical  Sciences  for  October,  1876,  in  a 
paper  entitled  “On  Functional  Spasms.”  From  it  we  abstract 
the  following  history : 

* For  further  particulars  concerning  these  interesting  phenomena  the  reader 
is  referred  to  the  original  paper. 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


125 


“ E.  C.,  aged  thirty-three,  watch  case-maker,  married.  No 
syphilis.  Family  history  bad.  A sister,  aunt,  and  grandmother 
had  palsies  in  middle  life ; an  uncle  had  epilepsy,  and  a cousin 
dementia.  He  was  always  nervous  and  excitable,  used  no  spirits, 
smoked  moderately,  and  was  always  well  until  the  summer  of 
1865,  when  he  was  two  days  unconscious  from  sunstroke,  and  has 
ever  since  been  made  weak  by  the  heat  of  summer.  About  two 
years  ago,  in  the  summer  of  1874,  he  observed  that  while  walking 
the  legs  felt  weak,  and  he  was  obliged  to  stop,  as  if  to  regain 
power ; after  which  the  right  leg  would  drag  for  a time.  At  the 
same  time  he  began  to  have  pain  in  the  back  of  the  neck  and 
lumbar  spine.  These  pains  continue.  In  January,  1875,  he  no- 
ticed a slight  but  increasing  tremor  in  the  left  arm,  and  in  two  or 
three  months  the  strange  condition  which  I shall  try  to  describe. 

u When  I first  saw  Mr.  C.  he  was  a healthy-looking  man,  of 
unusual  intelligence,  and  marvellously  patient  under  his  great 
suffering.  In  sleep  there  was  no  movement ; when  he  awakened 
he  was  conscious  of  the  left  hand  being  rigidly  closed.  In  a few 
moments  it  began  to  twitch,  the  fingers  moving  as  do  those  of  a 
violin-player.  The  slightest  movement  of  any  other  limb,  speak- 
ing, or  eating — even  if  he  be  fed — causes  the  left  arm  to  execute 
a constant  motion  of  striking  the  bed  or  his  side,  the  limb  being 
the  while  extended.  When  he  arose  and  walked,  this  action  be- 
came more  violent,  and  so  much  resembled  the  steady,  rapid 
movement  of  a pendulum,  that  I spoke  of  it  at  once  to  my  assist- 
ants as  a case  of  what  might  be  called  pendulum  spasms.  In  fact, 
its  rhythmic  regularity  was  astonishing.  Dr.  Sinkler  timed  it,  on 
one  occasion,  as  one  hundred  and  fifty-seven  (in  a minute);  and 
on  several  others  I found  it  always  exactly  one  hundred  and 
sixty.  It  was  as  accurate  as  the  heart  in  its  motion,  but  certain 
things  always  increased  either  the  power  or  the  number  of  the 
motions.  Thus,  if  he  stood  up,  having  been  seated,  the  number 
did  not  alter,  but  the  force  of  the  blow  on  the  thigh  increased 
remarkably. 

“ If  while  standing  he  elevated  and  extended  the  right  hand 
and  arm  to  the  shoulder  level,  instantly  the  rhythm  mounted  to 
two  hundred  ; and  when  the  right  arm  ceased  to  act  the  number 
fell  again  speedily  to  one  hundred  and  sixty. 

“ When  there  was  no  pendulum  spasm  he  could  perform  with 


126 


A STUDY  OF  SOME 


the  left  arm  any  voluntary  act  not  involving  the  hand,  which 
itself  never  ceased  to  twitch  ; but  while  the  swinging  spasms 
lasted  he  could  execute  no  volitional  act,  and  the  effort  to  move 
the  limb  enormously  increased  the  spasms. 

“ Excitement  and  emotion  and  all  forms  of  electricity  added 
to  the  force  of  the  motions,  but  voluntary  movements  of  other 
limbs  increased  the  number  more  than  the  force.  Attempts  at 
passive  motion,  as  the  effort  to  fully  extend  the  partially-flexed 
fingers,  cause  intense  pain  in  the  occiput,  just  as  the  effort  to 
overcome  rigid  gastrocnemii  in  certain  cases  gives  rise  to  pain  in 
the  dorsal  spine.  He  has  the  power  to  stop  the  spasms  by  certain 
manoeuvres.  If  he  seizes  the  left  hand  with  the  right  and,  flexing 
the  left  arm,  holds  it,  there  is  a kind  of  general  spasm ; the  left 
hand  for  a moment  seems  to  struggle  with  increasing  violence ; 
he  totters ; the  face  is  convulsed ; there  is  horrible  pain  in  the 
back  of  the  head.  Then  he  gently  releases  the  left  arm,  which, 
save  for  a slight  tremor  or  twitching  of  the  unquiet  fingers,  re- 
mains at  rest,  and  may  not  move  in  violent  spasm  for  an  hour  or 
more,  and  is  sometimes  nearly  still  for  twelve  hours. 

“ He  avoids  the  use  of  one  hand  to  stop  the  other,  because  of 
the  great  pain  it  causes  in  the  head.  When  he  stops  the  hand 
with  his  leg  he  has  little  head  pain,  but  it  is  altogether  so  un- 
pleasant for  him  to  check  it  that  he  rarely  does  so.  When  stand- 
ing, if  he  wishes  to  stop  the  pendulum  spasm,  he  throws  the  left 
leg  back  so  as  to  trip  the  toe ; the  arm  then  falls  in  as  it  moves, 
and  he  brings  the  leg  forward  so  as  to  catch  the  arm  against  the 
thigh,  where  its  own  spasm  holds  it.  Then  there  is  a general 
convulsive  movement  of  the  entire  body,  and  the  limb  is  at  rest. 

“ When  the  arm  is  hanging  quiet  at  his  side,  it  begins  to  move 
if  he  walks  a few  steps,  or  if  he  lifts  the  right  arm,  in  which  at 
times — especially  after  sudden  arrest  of  the  spasm — I noticed 
some  large  tremor. 

“ In  all  of  this  strange  set  of  symptoms  there  is  no  loss  of  con- 
sciousness, no  ansesthesia,  no  ocular  trouble  or  spasm,  no  aural 
defect.  When  he  walks  long  or  fast  the  legs  have  some  dis- 
position to  become  rigid,  but  this  is  an  inconstant  feature.” 

Since  this  graphic  account  was  published,  the  phenomena  pre- 
sented have  undergone  some  changes.  The  simple  pendulum 
movement  is  now  replaced  by  a more  complex  rotary  movement, 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


127 


and  which  is  present  only  under  certain  conditions.  Thus,  when 
Mr.  C.  is  sitting  or  standing  still,  the  arm  is  carried  in  a semi- 
flexed  position,  while  the  hand  and  fingers  are  markedly  con- 
tracted and  in  constant  vibration.  Were  it  not  for  this  last  factor 
— namely,  the  vibration — the  position  would  bear  some  resem- 
blance to  that  assumed  by  patients  suffering  from  secondary  con- 
tracture. 

If  Mr.  C.,  however,  attempts  to  rise  or  to  walk,  the  forearm 
becomes  slightly  less  flexed,  whilst  the  vibration  increases  both  in 
amplitude  and  rapidity.  If  the  walk  be  persisted  in,  and  be  it 


ever  so  slow  and  gentle,  the  forearm  finally  becomes  completely 
extended,  and  now  the  entire  arm  describes  a rotary  motion,  such 
as  is  depicted  in  the  upper  series  of  Plate  557,  and  in  Fig.  19. 

It  will  be  observed  that  this  movement  is  one  in  which  the 
hand,  while  it  is  suspended  from  the  shoulder  like  a pendulum,  de- 
scribes a circle  by  first  sweeping  forward,  then  outward,  then  back- 
ward, and,  finally,  forward  again  to  its  original  position.  Fig.  19 
illustrates  the  extent  of  this  movement  in  the  outward  direction. 

If,  now,  wdiile  the  arm  is  performing  this  peculiar  movement, 
Mr.  C.  attempts  to  raise  the  arm  up  to  the  shoulder,  the  rotary 
movement  increases  wonderfully  in  extent.  {Vide  Plate  557, 
middle  series.)  The  arm  describes  a circle,  indicated  by  the 

9 


128 


A STUDY  OF  SOME 


arrows  in  Fig.  20,  which,  like  Fig.  19,  is  the  result  of  superim- 
posed tracings  of  the  individual  pictures.  The  arm  extended, 
and  the  hand  and  fingers  contracted,  describe  a circle  in  front  of 
the  body.  The  hand  sweeps  upward  and  inward,  passes  the  face, 
sweeps  upward  and  outward,  then  downward,  and  then  inward 
again  to  its  original  position. 

At  the  same  time  that  this  spasm  of  the  left  arm  is  taking 
place  the  right  arm,  too,  becomes  convulsed.  ( Vide  Fig.  20.)  It 
is  raised  abruptly,  and  the  forearm  directed  upward,  and  a series 
of  to-and-fro  movements  commence,  and  which  examination  shows 
are  synchronous  with  the  rotary  movement  of  the  opposite  limb. 
As  the  rotating  limb  rises,  the  right  arm  rises;  as  the  former  de- 
scends, the  latter  descends.  As  the  left  arm  sweeps  inward  and 
upward,  the  right  arm  steadily  ascends ; as  the  left  arm  goes  out- 
ward and  downward,  the  right  arm  steadily  descends.  There  is 
certainly  here  a curious  association  of  movement. 

If,  instead  of  raising  the  arm  to  the  shoulder,  Mr.  C.  simply 
sharply  flexes  the  left  forearm  at  the  time 
it  is  rotating,  as  in  Fig.  21,  a series  of 
to-and-fro  movements  replace  the  rotary 
movements.  ( Vide  third  series,  Plate 
557,  and  Fig.  21.)  That  is,  the  left  arm 
is  thrown  violently  backward  and  for- 
ward. At  the  same  time  the  right  arm 
becomes  similarly  affected,  and  it,  too,  is 
thrown  violently  backward  and  forward. 
As  in  the  previous  experiment,  the  move- 
ments are  found  to  be  synchronous. 

It  will  be  observed  that  at  no  time 
does  the  right  hand  become  contracted 
and  the  fingers  “ clawed.” 

Some  idea  may  be  gained  of  the  rapid- 
ity of  these  movements  when  we  reflect 
that  the  complete  cycle  of  the  movement  represented  in  Fig.  19  occu- 
pied less  than  .47  part  of  a second,  while  in  Fig.  20  the  rapidity  had 
so  much  increased  that  the  cycle  occupied  only  .32  of  a second.* 


* The  intervals  of  time  between  the  positions  of  the  upper  series  of  Plate 
557  were  .048  of  a second.  The  entire  movement  is  included  in  ten  pictures. 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


129 


In  Plate  556  farther  interesting  details  of  this  case  are  illus- 
trated. 

If  Mr.  C.  is  sitting  quietly  in  a chair,  with  the  arm  in  the 
semiflexed  position  already  described,  and  then  lies  down  with 
his  back  and  head  flat  upon  the  ground,  all  vibration  in  the  hand 
ceases.  It  becomes  perfectly  quiet,  and  he  can  execute  with  it 
most  exact  and  delicate  voluntary  movements.  If,  however,  he 
now  attempts  to  raise  the  head,  violent  tremor  at  once  appears  in 


Fig.  22. 


the  hand.  (See  Fig.  22.)  This  tremor  is  so  violent  that  the  feet 
and  head  are  affected.  It  is  remarkable  that  raising  of  the  head 
is  the  only  movement  that  provokes  the  tremor.  Raising  the 
right  hand  or  either  foot  has  no  effect. 


Fig.  23. 


Similarly,  if  Mr.  C.  lie  upon  the  ground  and  the  motion  be 
completely  arrested,  it  is  again  violently  excited  by  striking  the 
patellar  tendon  (see  Fig.  23,  and  series  second  of  Plate  556)  or  by 
attempting  to  elicit  ankle  clonus. 


The  duration  of  exposure  for  each  individual  picture  was  less  than  .004 
second.  The  sum  total  of  the  nine  intervals  and  ten  exposures  is  (.43  -f-  .04  = 
.47)  equal  to  .47  of  a second.  In  series  B,  Plate  557,  six  positions  complete  the 
movement. 


130 


A STUDY  OF  SOME 


It  is  also  a remarkable  fact  that  the  tremor  so  excited,  or  excited 
by  raising  the  head,  cannot  be  quieted  unless  Mr.  C.  arises  com - 
pletely  from  the  ground  and  lies  down  anew. 

It  is  not  within  the  province  of  this  monograph  to  speculate 
upon  this  interesting  case.  However,  a point  that  is  of  exceed- 
ingly  great  interest  is  the  diffusion  of  the  convulsive  movement 
to  other  parts  of  the  body,  notably  to  the  other  arm.  This  fact 
is  exceedingly  suggestive  with  regard  to  the  spreading  of  the 
tremor  or  clonic  spasm  in  the  artificially-induced  convulsions.  It 
seems  as  though  at  times  the  opposite  arm  was  obliged  to  take  up 
an  overflow  of  nerve-force. 

It  should  be  stated  that  Mr.  C.  is  still  able  to  arrest  the  move- 
ment of  the  left  arm,  at  least  in  part,  by  seizing  it  by  the  right 
hand,  very  much  in  the  manner  described  by  Dr.  Mitchell. 


Wheel- Photographs  of  Tremors . 

Mr.  Muybridge  having  at  his  command  a “ Marey”  wheel,  the 
writer  resolved  to  test  the  possibility  of  photographing  tremors. 
The  wheel,  which  contained  eight  fenestra,  revolved  before  the 
camera  five  times  in  two  seconds,  so  that  in  the  course  of  one 
second  twenty  exposures  could  be  made,  or,  in  other  words,  the 
interval  of  time  between  any  two  exposures  was  equivalent  to 
one-twentieth  of  a second. 

The  first  case  selected  was  one  of  typical  paralysis  agitans . It 
was  a woman,  fifty-six  years  of  age,  who  gave  the  following  his- 
tory : About  four  years  ago  she  had  intense  pain  in  the  ankles 
and  shoulders.  She  described  it  as  rheumatism.  The  ankles 
were  much  swollen.  After  the  pain  subsided,  she  began  to  have 
shaking  or  trembling,  especially  in  the  left  arm.  It  was  not  at 
that  time  marked,  if  at  all,  in  any  other  portion  of  the  body. 
At  the  time  the  photographs  were  made,  however,  the  tremor  af- 
fected both  arms  about  equally.  She  complained  of  burning 
pain  in  the  shoulders.  The  position  she  assumed  was  typical  of 
an  advanced  stage  of  the  disease.  When  standing,  the  trunk  and 
head  were  thrown  forward,  the  forearms  partially  flexed  on  the 
arms,  and  the  hands  and  fingers  bent  into  the  “ writing  hand.” 
The  latter  was  in  a constant,  regular  tremor.  When  she  was 
asked  to  move  the  arms,  it  was  noticed  the  movements  were  ex- 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


131 


tremely  slow  and  that  the  arms  were  very  stiff.  When  she  was 
asked  to  walk  she  showed  a marked  tendency  to  fall  forward. 

The  head  was  not  affected  by  the  tremor,  and  was  carried  in  a 
rigid,  fixed  position.  The  patient  never  turned  her  head  unless 
specially  asked  to  do  so. 

The  tremor  appeared  quite  rhythmical,  and  when  the  writer 
first  saw  the  patient  it  entirely  disappeared  upon  voluntary  move- 
ment. Later  on,  and  at  the  time  of  making  the  photographs,  it 
ceased  to  disappear  altogether,  though  it  grew  much  less. 

In  making  the  experiment,  the  patient,  as  in  Marey’s  experi- 
ments on  the  normal  walk,  was  dressed  in  a suit  of  dark-blue 
tights.  On  these  a white  stripe  ran  along  the  outside  of  the  arm 
from  the  shoulder  to  the  wrist  and  hand,  upon  which  a bright 
metallic  button  was  sewed.  The  legs  were  similarly  striped.  The 
patient  w’as  then  seated  on  a chair,  and  at  a given  signal  she  raised 
both  the  arm  and  leg  of  one  side.  The  result  is  shown  in  Figs. 
24  and  25. 


Fig.  24.  Fig.  25. 


In  Fig.  24,  the  patient  started  to  raise  the  arm  a little  after  the 
exposures  with  the  wheel  had  commenced,  consequently  the  stripe 
down  the  arm  was  heavily  photographed,  and  the  two  bright  dots 
seen  at  its  lower  end  correspond  to  the  rapidly- vibrating  button 
on  the  hand.  Each  successive  stripe  from  below  upward  is  still 
tipped  by  a double  dot,  though  the  dots  appear  slightly  closer 
together.  The  interval  between  the  dots  is  of  course  blurred. 

Another  interesting  fact  is  illustrated  by  this  photograph.  The 
movement  consisted  in  raising  the  hand  to  a level  with  the  top  of 
the  head.  It  is  noticed  that  the  movement  is  commenced  slowly 


132 


A STUDY  OF  SOME 


and  with  apparent  difficulty.  The  first  line  above  the  heavy 
white  stripe  is  almost  in  contact  with  the  latter,  and  cannot  be 
seen  except  upon  close  inspection.  Thence  the  intervals  between 
the  various  lines  gradually  increase  until  towards  the  completion 
of  the  movement,  when  they  again  appear  to  diminish.  Though 
this  increase  of  rapidity  of  movement  and  subsequent  decrease  is 
the  same  in  principle  as  that  which  takes  place  normally,  still  the 
slowness  of  the  start  and  the  slowness  of  the  entire  movement 
are  remarkable.  For  instance,  the  arm  sweeps  over  thirteen  in- 
tervals before  the  stripe  touches  the  chin  and  nose, — that  is, 
counting  up  to  the  upper  impression  of  the  face,  as  during  the 
movement  the  patient  threw  her  head  and  shoulders  backward. 
The  thirteen  intervals  correspond  to  or  about  two-thirds  of  a 
second.  Therefore  it  took  the  patient  all  of  this  time  to  move  her 
hand  up  to  a level  of  the  face,  although  she  was  told  to  move  as 
quickly  as  possible. 

No  tremor  is  noticed  in  the  leg  or  foot.  In  Fig.  25  the  arm 
and  foot  were  also  raised  at  the  same  time  and  then  brought 
down  again.  No  tremor  is  noticed  in  the  foot,  but  both  in  the 
ascent  and  descent  of  the  arm  the  double  rows  of  dots  are  plainly 
seen. 

This  persistence  of  the  tremor  of  paralysis  agitans  during  vol- 
untary movement  is  a matter  of  considerable  importance  from 
the  diagnostic  point  of  view.  It  is  generally  accepted  that  one  of 
the  chief  diagnostic  features  of  the  disease  is  the  cessation  of 
the  tremor  during  voluntary  movement.  This  was  certainly  the 
case  when  the  patient  was  first  seen,  but  as  the  disease  progressed 
the  cessation  no  longer  took  place,  and  this  is  proven  by  the 
photograph. 

The  other  case,  photographed  by  means  of  the  “ Marey  wheel,” 
was  a man,  aged  sixty-five,  who  had  been  incapacitated  from  work 
for  about  seven  months  by  reason  of  a tremor  of  the  right  hand. 
The  case  appeared  to  be  one  of  commencing  paralysis  agitans , 
although  some  of  the  symptoms,  such  as  rigidity  and  festi nation, 
were  not  typical. 

The  photograph  of  Fig.  26  was  made  in  exactly  the  same 
manner  as  the  preceding  ones,  with  the  exception  that  the  patient 
wore  the  white  stripe  upon  the  arm  only.  There  was  a metallic 
button  on  the  shoulder,  at  the  elbow,  and  on  the  hand.  He  was 


NORMAL  AND  ABNORMAL  MOVEMENTS. 


133 


seated  upon  a chair  and  told  to  rise  at  a given  signal.  His  right 
hand  was  resting  on  the  chair  just  where  the  arched  piece  of  the 
back  is  joined  to  the  seat. 

When  everything  was  in 
readiness  he  was  told  to 
rise.  The  tremor  which 
had  been  marked  while 
the  hand  was  resting  on 
the  chair  gradually  be- 
came less  and  less  evident, 
and  finally  ceased  when  the 
erect  position  was  reached. 

In  Fig.  26  the  lower 
row  of  dots  is  seen  to  be 
double  at  the  beginning  of 
the  act,  thus  showing  the 
presence  of  tremor.  As 
the  man  approaches  the  erect  position  the  dots  are  gradually  less 
widely  separated  and  finally  coalesce.  In  the  case  of  the  elbow, 
and  also  of  the  shoulder,  a single  continuous  row  of  dots  alone  is 
seen. 

From  the  above  figures  it  is  very  evident  that  a properly  con- 
structed “ Marey  wheel”  offers  a valuable  and  accurate  method  of 
studying  not  only  tremors  but  probably  also  other  forms  of  abnor- 
mal movement. 


Fig.  26. 


The  man  is  in  the  act  of  rising  and  walking  forward. 
A bright  button  is  fixed  upon  the  hand.  The  double 
row  of  dots  indicate  the  tremor  of  the  hand. 


ADDENDUM. 

In  Mr.  Muybridge’s  catalogue  a number  of  the  clinical  plates  are  incor- 
rectly designated. 

Plate  549  should  be  “ Locomotor  Ataxia.” 

Plate  555  should  be  “ Muscular  Atrophy  of  Left  Leg.” 

Plate  558  should  be  “Stuporous  Melancholia.” 

Plate  559  should  be  “ Partial  Paraplegia.” 


INDEX. 


Action  of  limb  in  “ going  off,”  49. 
Age,  factor  of  disturbance,  57. 

Ape,  42. 

Aphrodite,  95. 

Armadillo,  45. 

Baboon,  42,  65,  74,  88. 

Backward  strain,  44. 

Bat,  92. 

Bear,  89. 

Body,  influence  of,  on  foot,  48. 
Buffalo,  Indian,  54. 

N.  A.,  64,  92. 

Camel,  47,  52,  92,  94. 

Capybara,  48,  51. 

Cat,  domestic  35,  54,  55,  64. 
Chimpanzee,  50. 

Chorea,  local,  124. 

Contact-motor  of  Muybridge,  23. 
Convulsions  artificially  induced,  122. 
Crocodile,  95. 

Deer,  Canadian,  38. 
fallow,  53,  62. 
mule,  60. 

Virginian,  35,  44,  45,  54,  88,  96. 
Degrees,  limb  movements  recorded 
in,  52. 

Dicotyles,  89. 

Dipus,  92. 

Dog,  43,  47,  52,  57,  58,  93. 

Eakins,  Prof.,  modified  Marey- wheel, 

10. 

Echidna,  54,  95. 

Effect  of  positions  on  head,  neck, 
trunk,  47. 

Elephant,  35,  45,  47,  49,  52,  53,  58, 
90. 

Evolution  of  gait,  94. 

Exposor  of  Muybridge,  18. 
Extremity,  anterior,  54. 

Eversion  of  foot,  50. 

Feet,  position  of,  in  “ recover,”  55. 
Flight,  99. 

Foot,  eversion  of,  50. 

striking  ground  on  outer  border, 
50. 


Gait,  contrasts  of,  66. 
evolution  of,  94. 
graphic  method  of  study,  67. 
heterochiral,  63. 
human,  97. 

in  lateral  sclerosis,  114. 
in  locomotor  ataxia,  110. 
intervals  in,  63. 

numerical  method  of  study,  62. 
quadruped,  61. 
synchiral,  61. 
transitions  in,  66. 

Gallop,  62. 

Giraffe,  45,  66. 

Goat,  48,  49. 

Guanaco,  94. 

Heel,  depression  of,  58. 
Hippopotamus,  61. 

Hog,  45,  55,  61,  88. 

Horse,  35,  45,  48,  49,  54,  55,  56,  58, 
63,  93,  96. 

Human  subject,  movements  of,  97. 

Inward  rotation,  58. 

Kangaroo,  40. 

Keel  on  metapodium,  94. 

Kicking,  act  of,  58. 

Lateral  sclerosis,  114. 

Laterals  in  rack,  67. 
in  walk,  67. 

Limb,  action  of,  disengaged,  97. 
angulation  of,  at  ankle,  55. 
oscillation  of,  98. 
rotation  of,  89. 

Limbs,  action  of,  40,  49. 
movement  of,  39. 
position  of,  40. 

position  of,  as  to  axis  of  trunk,  58. 
work  done  by,  40. 

Lion,  47,  52. 

Locomotor  ataxia,  110. 

Man,  normal  walk  of,  104. 

Mane,  93. 

Manner  of  limb  going  “off”  in 
spring,  45. 


135 


136 


INDEX, 


Marey-wheel,  Eakins’s  modification 
of,  10. 

Metapodium,  keel  on,  94. 

Minor  peculiarities,  91. 

Motions  same  in  all  quadrupeds,  43. 
Movements,  human  subject,  97. 
limbs,  39. 

oblique,  and  numbers  of  toes,  89. 

Nerita,  95. 

Oryx,  62. 

Oscillation,  96. 

Ox,  35,  45,  54,  55,  64. 

Pecora,  91. 

Potomogale,  95. 

Rabbit,  37. 

Raccoon,  35,  38,  43,  44,  47,  48,  64,  65, 
67,  72. 

Rack,  66. 

Reptile,  95. 

Rhinoceros,  96. 

Rotation,  inward,  58. 

Salamander,  40. 

Serpent,  59. 

Sldn-folds,  93. 


Skunk,  35. 

Sloth,  35,  38,  42,  52,  78. 

Slowing  up,  55. 

Solenodon,  55. 

Studio,  plan  of,  at  Univ.  of  Penna. 
17. 

Superficies,  characters  of,  92. 

Sus,  89. 

Terms,  use  of,  36. 

Tiger,  47. 

Toes,  length  of,  48. 

obliquity  of,  48. 

Torsion  of  trunk,  45,  57. 

Training,  factor  of  disturbance,  57. 
Tremors,  wheel-photographs  of,  130. 
Trot,  65. 

Turning  round,  47. 

Turtle,  39. 

Tylopoda,  91. 

Walk,  combinations  in,  64. 
normal,  of  man,  104. 
quadruped,  63. 

support  of  vertebral  column  in 
65. 

Wombat,  47. 

Zoological  considerations,  84. 


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